Question

Carlos 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 did not distribute correctly
He combined like terms incorrectly, it should have been 4x instead of 5x
He made no mistake

Could someone help me figure this out please?

Answer 1

B.