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

He should have substituted 5 + 2x

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

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

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




 He should have substituted 5 + 2x

 He combined like terms incorrectly, it should have been 4x instead of 5x

 He subtracted 10 from the right side instead of adding 10 to the right side

 He made no mistake

anonymous · Answer

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

anonymous · Answer

@sumsumjoe 

he subtracted 10 from the right side, instead of adding 10...

cause, it should be 5x = 20...not 0.