20=-6+2(f+8)

Solution for 20=-6+2(f+8) equation:

Simplifying
20 = -6 + 2(f + 8)

Reorder the terms:
20 = -6 + 2(8 + f)
20 = -6 + (8 * 2 + f * 2)
20 = -6 + (16 + 2f)

Combine like terms: -6 + 16 = 10
20 = 10 + 2f

Solving
20 = 10 + 2f

Solving for variable 'f'.

Move all terms containing f to the left, all other terms to the right.

Add '-2f' to each side of the equation.
20 + -2f = 10 + 2f + -2f

Combine like terms: 2f + -2f = 0
20 + -2f = 10 + 0
20 + -2f = 10

Add '-20' to each side of the equation.
20 + -20 + -2f = 10 + -20

Combine like terms: 20 + -20 = 0
0 + -2f = 10 + -20
-2f = 10 + -20

Combine like terms: 10 + -20 = -10
-2f = -10

Divide each side by '-2'.
f = 5

Simplifying
f = 5