42=-2f

Solution for 42=-2f equation:

Simplifying
42 = -2f

Solving
42 = -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.
42 + 2f = -2f + 2f

Combine like terms: -2f + 2f = 0
42 + 2f = 0

Add '-42' to each side of the equation.
42 + -42 + 2f = 0 + -42

Combine like terms: 42 + -42 = 0
0 + 2f = 0 + -42
2f = 0 + -42

Combine like terms: 0 + -42 = -42
2f = -42

Divide each side by '2'.
f = -21

Simplifying
f = -21