Answer:
80cm^2
Step-by-step explanation:
20*5=100
10*2=20
100-20=80
Answer: g(f(x)) = g(x²-7)=x
Step-by-step explanation:
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:

Answer:
B and C
Step-by-step explanation: