Question

If 4x+7=12 what is the value of 8x+3

Answer 1

There is actually 2 ways to solve this, I will show you both.

The first is obvious, solve for x in the first one, and plug it into the 2nd one and get the answer

4x + 7 = 12

4x = 5

x =
`(5)/(4)`

8(
`(5)/(4)`) + 3

2 * 5 + 3

10 + 3

13

The 2nd option is to manipulate the 4x + 7 to be 8x + 3

4x + 7 = 12

start by moving the 7 over

4x = 5

multiply both sides by 2

8x = 10

and add 3 to both sides

8x + 3 = 13

Answer 2

Solve for x in the equation then plug it into the expression.

1. 4x + 7 = 12
2. 8x + 3

4x + 7 = 12

• Subtract 7 from both sides.

4x = 5

• Divide both sides by 4.

x = 5/4

• Plug 5/4 for x into 8x + 3.

8(5/4) + 3 = 13

13

• is your answer.