Number word problem: The second of three numbers is...

[student44]

I have a page of word problems that I can't do! Could you solve one problem so that I can see how to do it? My teacher wants us to try and figure them out, but I can't get the right answers. We have the answers for the problems, I just can't get to them!

"The second of three numbers is 8 more than the first, and the third number is 3 less than 3 times the first. If the third number is 15 more than the second, find the three numbers." I keep getting -2. The correct answer is 14, (22, 37 for the last two numbers). Help!

 

[stapel]

I keep getting -2.

Please reply showing all of your steps.

Thank you.

Eliz.

 

[student44]

reply

our steps were:
#1) x
#2) x+8
#3) 3x-3

x+8=3x+-3+15
x+8=3x+12
-12+(x+8)=(3x+12)+-12
-x+x+-4=3x+-x
-4=2x
1/2*-4=1/2*2x
-2=x
x=-2

 

[skeeter]

Re: reply

our steps were:
#1) x
#2) x+8
#3) 3x-3

x+8=3x+-3+15 here is the mistake, the equation should be
x+8 = (3x-3) - 15 ... the 3rd number is 15 more than the 2nd, you have to subtract 15 from the 3rd number to make it equal to the 2nd.
x+8=3x+12
-12+(x+8)=(3x+12)+-12
-x+x+-4=3x+-x
-4=2x
1/2*-4=1/2*2x
-2=x
x=-2

 

[Denis]

I"The second of three numbers is 8 more than the first, and the third number is 3 less than 3 times the first. If the third number is 15 more than the second, find the three numbers." I keep getting -2. The correct answer is 14, (22, 37 for the last two numbers).

The correct answer is NOT 14, 22, 37 ; 14 * 3 - 3 = 39

x, x + 8, 3x - 3

3x - 3 = x + 8 + 15
2x = 26
x = 13 ; so 13, 21, 26

 

[student44]

Thank you so much! Now I understand what I did wrong on all the problems!! :lol: