42=C+.40C

Solution for 42=C+.40C equation:

Simplifying
42 = C + 0.40C

Combine like terms: C + 0.40C = 1.4C
42 = 1.4C

Solving
42 = 1.4C

Solving for variable 'C'.

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

Add '-1.4C' to each side of the equation.
42 + -1.4C = 1.4C + -1.4C

Combine like terms: 1.4C + -1.4C = 0.0
42 + -1.4C = 0.0

Add '-42' to each side of the equation.
42 + -42 + -1.4C = 0.0 + -42

Combine like terms: 42 + -42 = 0
0 + -1.4C = 0.0 + -42
-1.4C = 0.0 + -42

Combine like terms: 0.0 + -42 = -42
-1.4C = -42

Divide each side by '-1.4'.
C = 30

Simplifying
C = 30