Question

how to solve this system of equations with substitution?

y= 4x
x + y = 5

Answer 1

X+4X=5
5X=5
5/5=1
X=1

Answer 2

y = 4x is equation1.

x + y = 5 can also be written to make y the subject.
y = 5 - x is equation 2

EQUATION 1 --> y = 4x
EQUATION 2 --> y = 5 - x
This basically means:
4x = 5 - x
4x + x = 5
5x = 5
x = 1