Expert: Lynn Houston - 10/1/2010

Question
hi, I am in 7th grade and 12 years old. I have a problem with this question: solve for x: (x-3)/y=x.
This is how far I got:
multiply both sides by Y, which would cancel out the Y, which becomes: x-3=xy. After this I am stuck, what is the next step? Is the answer x=3/(y-1). Please help. Thanks.

Answer
You're on the right track. To solve for x, you need to "undo" everything that has been done to x, so, x-3 was divided by y, so you need to multiply by y to "undo" that function.  Now you have

x-3 = xy, divide both sides by x
x/x-3/x = y  x/x = 1 so
1-(3/x) = y   subtract 1 from both sides
-3/x = y-1  multiply both sides by x
-3 = x(y-1)  divide by y-1
- 3/y-1 = x

The only thing you forgot was the negative. Make sense?