Question

substitution method
{x+y=10
{ y=4x

Answer 1

For one moment, I thought this was a programming question. Substitute y=4x into x+y=10 to get x+4x=10. Simplify this and you obtain 5x=10, which is the same thing as x=2. Now, plug this into the second equation to solve for y and you get y=8.

Answer 2

Therefore, the only point which satisfies this system is (2, 8).