Question

How do you solve x + x + x√2=10?

I did x^2 + x^2 + 2x^2 = 100
4x^2 = 100

How do I continue?

Answer 1

I'll be honest, I don't know if you are right in the beginning. I can, however, tell you how to continue from 4x^2=100, if you are right up until that point.
4x^2=100
Divide both sides by 4.
x^2=25
Take the square root of both sides.
x=+-5

Answer 2

14x - 2y = 78
2x - 2y = 6