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

Answer 1

he didn't distribute the negative in front of the 2 which messed up the rest of the steps

x - 2(5 - 2x) = 10
x - 10 + 4x = 10
5x = 10 + 10
5x = 20
x = 4