I'm having difficulty solving 0.7y+9=y+15?????

Question

I know the answer is 20 but can't remember procedure.
Do I change the decimal to a fraction 1st???

Answer 1

getting rid of decimals and fractions is usually a good first step. In this case, we get

7y + 90 = 10y + 150
-3y = 60
y = -20

it could have been done without that. the procedure is to collect all the y's on one side, and the numbers on the other

.7y - y = 15 - 9
-.3y = 6
y = 6/-.3
y = -20