# Logic

##### Full Member
x,y is variables, "=" is equal like math "=" ..nothing else.
what's struggling me is: yeah x=y right? but who will ensure for me that if I progress in my analysis and arrived to y=z, that's x=y still right? if so then we can say x=z ! but if I didn't change the equation x=y who ensure for me that it's really didn't change that equation and still right for any circumstances ?!

what's confusing me this:
(1) x=y ..so fine with that.
after 5minutes of thinking and analysing problem, I get
(2) y=z

then we conclude that x=z, but what's confusing me why it's that right? who ensures that the first equation is still right and none changed it?! that's what confusing me alot!!!

#### Ryan$##### Full Member Is that book written in English? (Maybe that's part of your issue.) If you and I have exactly$1 in our pocket, and somebody else says to you, "I have exactly $1 in my pocket, just like you", then why think the$1 in my pocket would suddenly change. Magic?

I'm totally with you, but in the second part who said that it didn't change?! that's my problem. if I didn't touch your pocket, then is it definitely still the same?!

I'm not saying magic, because there's no magic in math. what I'm thinking that none tells that you didn't change what's in your pocket after a while (after we read and finish the second part of your sentence..maybe the first case(your pocket) would be changed ! because a time have passed since we have read your first statement), so how I know that's still $1 in your pocket?!! #### Denis ##### Senior Member I'm not saying magic, because there's no magic in math. what I'm thinking that none tells that you didn't change what's in your pocket after a while (after we read and finish the second part of your sentence..maybe the first case(your pocket) would be changed ! because a time have passed since we have read your first statement), so how I know that's still$1 in your pocket?!!
Ryan, if I was a moderator, I'd "close" such ridiculous threads....

##### Full Member
Ryan, if I was a moderator, I'd "close" such ridiculous threads....
and instead of just bothering, it could be more than appreciated and honor to help your OP no more nothing else, yeah it might be a silly question, but I face a problem with it which related to me it's magnificent problem, thanks alot

#### Otis

##### Senior Member
… who said that [given information] didn't change?! that's my problem …
… maybe the [amount of money in your pocket] changed ! because a time have passed since we have read your first statement …
If any of the dollar amounts (in my example) had changed, then you would have been told, already. So, don't worry about given information changing. Just accept the information in exercises as described.

In your exercise, it's given that x=y and y=z, so those relationships are fixed. Nothing about them is going to change, in that exercise.

If you worry that given information might change, then you won't be able to believe anything! An exercise statement will tell you, if anything changes.

In summary: Do not change given information.

##### Full Member
To be more clear that who would think that I opened this thread for troll !

I wasn't really known that we can't "simply" change the given information .. I though I could change it because in generally all possibilities would be happen.
thanks you once again to clear out that "DONT CHANGE GIVEN INFORMATION"

#### Denis

##### Senior Member
HEY Ryan, if 3 + 2 = 5, then 2 + 3 = ?

##### Full Member
If any of the dollar amounts (in my example) had changed, then you would have been told, already. So, don't worry about given information changing. Just accept the information in exercises as described.

In your exercise, it's given that x=y and y=z, so those relationships are fixed. Nothing about them is going to change, in that exercise.

If you worry that given information might change, then you won't be able to believe anything! An exercise statement will tell you, if anything changes.

In summary: Do not change given information.

Hi otis, pardon me about something to add
then I can say whenever I conclude something or given in the question itself, then it's fixed and there's no real life consequences like if x=6 and we moved to the next statements of the question itself, then if we want to use x, then x=6, there's no possibility that someone could changed it without given any information about ... Yeah?!