how do i solve the system using substitution?

Question

Solve the system using substitution x=4y+8 and  x=-5y-1.

Answer 1

Substitution method

Given equations are x = 4y+8 ---> (1)

x = -5y-1 ---> (2)

From (2) substitute the x value in (1).

-5y-1 = 4y+8

Subtract 4y from each side.

-5y-4y-1 = 4y-4y+8

-9y-1 = 8

Add 1 to each side.

-9y = 9

Divide to each side by negitive 9.

-9y/-9 = 9/-9

y = -1

Substitute the y value in (1).

x = -4+8

x = 4

Solution x = 4, y = -1.