Another problem kind of like the same one I posted... but got answer wrong

Kimbersqk

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Feb 4, 2012
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I tried completely solving this one like I was told how to do the last one but got the wrong answer.. Where did I go wrong?

1/5(5y+10)-9=-1/3(9y-15) <-- Original problem.

3(5y+10)-27=-5(9y-15) <-- For the first side I multiplied by 3 for a LCD of 15. Second side multiply by 5
15y+30-27=-45y+75 <-- I distributed 3*5, 3*10. -5*9, -5*-15.
15y +3=-45y+75 <-- Combined like terms.
+45y-3=+45y - 3 <-- Getting everything straightened out on each side.
60y =72
-- --
60 60 <-- dividing

y=1 12/60
y=1 1/5

My program(it is online math program) says 1 1/5 is wrong. Why?
 
I tried completely solving this one like I was told how to do the last one but got the wrong answer.. Where did I go wrong?

1/5(5y+10)-9=-1/3(9y-15) <-- Original problem.

3(5y+10)-27=-5(9y-15) <-- For the first side I multiplied by 3 for a LCD
That is your mistake.
It should be \(\displaystyle (-9)(15).\)
 
That is your mistake.
It should be \(\displaystyle (-9)(15).\)

Why would you do -9*15? I don't understand the reasoning for it. I know the LCD is 15, however, why would I multiply -9*15? You multiply 1/5*3 to get the LCD of 15 on both sides. Wouldn't you do the same for the -9? That is how I got -9*3=-27
 
Why would you do -9*15? I don't understand the reasoning for it. I know the LCD is 15, however, why would I multiply -9*15? You multiply 1/5*3 to get the LCD of 15 on both sides. Wouldn't you do the same for the -9? That is how I got -9*3=-27

Instead I would set it up as:

3(5y+10)-135=-5(9y-15)
15y+30-135=-45y+75
15y - 105=-45y + 75
+45y+ 105=+45y+105
60y = 180
--- ---
60 60

y=3

Is that right?
 
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