Question

Given the function f(x) = 2(x + 4), find x if f(x) = 20.

6

48

14

8

Answer 1

6

Explanation:

20=2(x+4)

Divide both sides by 2.

20/2 =x+4

Divide 20 by 2 to get 10.

10=x+4

Swap sides so that all variable terms are on the left-hand side.

x+4=10

Subtract 4 from both sides.

x=10−4

Subtract 4 from 10 to get 6.

x=6

Answer 2

So since we are solving for x, put 20 instead of f(x):

20 = 2(x + 4)

You can distribute 2 to x and 4:

20 = 2x + 8

Subtract both sides by 8:

12 = 2x

Divide both sides by 2

6 = x