What the answer subtitution of x=6+y and ×-4y=21

X= 6 + y
x - 4y= 21

The first equation is already solved for x. Take the value of x (6 + y) and substitute it for the x value in the second equation.

x - 4y= 21
(6 + y) - 4y= 21
combine like terms
6 - 3y= 21
subtract 6 from both sides
-3y= 15
divide both sides by -3
y= -5

Substitute the -5 for y in the equation to solve for x

x - 4y= 21
x - 4(-5)= 21
x + 20= 21
subtract 20 from both sides
x= 1

CHECK:
x= 1
y= -5

x= 6 + y
1= 6 + (-5)
1= 1

ANSWER: x= 1 and y= -5

Hope this helps! :)