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

Answer 1

he subtracted 10 instead of added it

Answer 2

shold have had 5 x -10 + 10 = 10 + 10
to give
5x = 20

Answer 3

y = 5 − 2x
x − 2(5 − 2x) = 10
x − 10 + 4x = 10
5x − 10 = 10......(u should add 10 to both sides)
5x =10+10
5x=20
x=4