Answer:
B
Step-by-step explanation:
The student's mistake was between Step 1 and Step 2.
Here, on the left side, they added 6x and 2x. The result should be 8x, not 4x.
It should be 8x-15=3x-75, not 4x-15=3x-75.
First they added 6x and 2x. They should not have subtracted it. The result should be 8x not 2.
