Question

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

Answer 1

The answer is He subtracted 10 from the right side instead of adding 10 to the right side

Let's solve it:
2x + y = 5
x − 2y = 10
________
Rearrange first equation to get y:
y = 5 - 2x
________
Substitute y into the second equation:
x - 2(5 - 2x) = 10
________
Multiply the terms:
x - 10 + 4x = 10
________
Combine the terms:
5x - 10 = 10
________
Add 10 on the both sides of the equation:
5x = 10 + 10
5x = 20
x = 4