Answer:
She made a mistake in Step 7.
Step-by-step explanation:
Step 1 through 6 are correct. Only from Step 6 to Step 7 the problem comes in: both sides of the equation are multiplied by x, however the x on the left side, by error, becomes 1. The correct state in Step 7 should look like this:

(f-g)(x) = 4x²-2x-12 which,evaluated at x=4, gives 64-8-12=44
X=9
3x-12=x+6
2x-12=6
2x=18
X=9
Answer:
RS = 10
Step-by-step explanation:
We are told that to get ∆QRS, the scale factor of ⅖ was used. To get side RS, we would multiply the side length of the side that corresponds to RS.
YZ corresponds to RS.
YZ = 25
Thus,
RS = 25*⅖
RS = 10