Question

Solve the system of linear equations by substitution.
x= 16-4y

3x+4y=8

Answer 1

Since given x = 16-4y
You can plug in 16-4y for x in the second equation: 3x + 4y = 8
3(16-4y) + 4y = 8
Now use distributive property
48-12y + 4y = 8
48 - 8y = 8
-8y = -40, y = 5
Now plug y = 5 into first equation
x = 16 - 4(5)
16-20 = -4, therefore x = -4

Solution: x = -4, y = 5
Or (-4,5)

Answer 2

x = - 4

y = 5

Explanation:

x = 16 - 4y Add 4y to both sides.

x + 4y = 16 Subtract x from both sides

4y = 16 - x

Now look at the second equation

3x + 4y = 8 Substitute the 4y in the equation above into this equation

3x + 16 - x = 8 Combine

2x + 16 = 8 Subtract 16 from both sides

2x = 8 - 16 Combine

2x = - 8 Divide by 2

2x / 2 = - 8/2

x = - 4

Use 3x + 4y = 8 to solve for y

Use 3(-4) + 4y = 8

-12 + 4y = 8 Add 12 to both sides

4y = 8 + 12 Combine

4y = 20 Divide by 4

4y/4 = 20/4

y = 5