Trevor solved the system of equations below. What mistake did he make in his work?

2x + y = 5
x − 2y = 10

y = 5 − 2x
x − 2(5 − 2x) = 10
x − 10 + 4x = 10
5x − 10 = 10
5x = 0
x = 0

2(0) + y = 5
y = 5

A. He should have substituted 5 + 2x

B. He combined like terms incorrectly, it should have been 4x instead of 5x

C. He subtracted 10 from the right side instead of adding 10 to the right side

D. He made no mistake

Question

Trevor solved the system of equations below. What mistake did he make in his work?

2x + y = 5
x − 2y = 10

y = 5 − 2x
x − 2(5 − 2x) = 10
x − 10 + 4x = 10
5x − 10 = 10
5x = 0
x = 0

2(0) + y = 5
y = 5

A. He should have substituted 5 + 2x

B. He combined like terms incorrectly, it should have been 4x instead of 5x

C. He subtracted 10 from the right side instead of adding 10 to the right side

D. He made no mistake

anonymous · Answer

@xuserx

marihelenh · Answer

The problem occurred in the 4th step.

anonymous · Answer

how?

marihelenh · Answer

To isolate the variable, he had to add 10 to the left side, which means he should have done that to the right side as well, but he subtracted it. The answer is C

anonymous · Answer

5x − 10 = 10
5x          = 20

anonymous · Answer

thank you