Teresa tried to find the solution to a system of equations with substitution but made an error in the process. After looking closely at Teresa's work, choose the answer that best describes the mistake she made. A. Teresa made an error in one of her first steps when she added 2x to both sides (she should have subtracted 2x from both sides).

B. Teresa should not have subtracted 1 from both sides of the equation when trying to find x, she should have added 1 to both sides.

C. During the last step in solving for x, Teresa should have divided both sides by -4 (not divided both sides by 5). X should equal -5/4.

D. When substituting the value for x into one of the equations, Teresa should not have multiplied the fraction by 3. She should have added 3 to the fractions.