8x-4y=-4

x=y-4

solve by substitution

x = 3, y = 7

Step-by-step explanation:

Solve the following system:

{8 x - 4 y = - 4

x = y - 4

Hint: | Perform a substitution.

Substitute x = y - 4 into the first equation:

{8 (y - 4) - 4 y = - 4

x = y - 4

Hint: | Expand the left hand side of the equation 8 (y - 4) - 4 y = - 4.

8 (y - 4) - 4 y = (8 y - 32) - 4 y = 4 y - 32:

{4 y - 32 = - 4

x = y - 4

Hint: | Choose an equation and a variable to solve for.

In the first equation, look to solve for y:

{4 y - 32 = - 4

x = y - 4

Hint: | Isolate terms with y to the left hand side.

Add 32 to both sides:

{4 y = 28

x = y - 4

Hint: | Solve for y.

Divide both sides by 4:

{y = 7

x = y - 4

Hint: | Perform a back substitution.

Substitute y = 7 into the second equation:

{y = 7

x = 3

Hint: | Sort results.

Collect results in alphabetical order:

Answer: {x = 3, y = 7

8x-4y=-4

8 (y-4) - 4y=-4

8y-32-4y=-4

8y-4y=-4+32

4y=28

y=28/4

y=7