Question

5x+y=27 y=4x using substitution method

Answer 1

Substitute 4x for y, and solve for x;
5x + (4x) = 27
9x = 27
x = 3
Substitute 3 in for x in the first equation and solve for y;
5(3) + y = 27
15 + y = 27
y = 12

Answer 2

 5x + y = 27
substitute: 5x + 4x = 27
combine: 9x = 27
divide (by 9): x = 3