39=42+x

Solution for 39=42+x equation:

Simplifying
39 = 42 + x

Solving
39 = 42 + x

Solving for variable 'x'.

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

Add '-1x' to each side of the equation.
39 + -1x = 42 + x + -1x

Combine like terms: x + -1x = 0
39 + -1x = 42 + 0
39 + -1x = 42

Add '-39' to each side of the equation.
39 + -39 + -1x = 42 + -39

Combine like terms: 39 + -39 = 0
0 + -1x = 42 + -39
-1x = 42 + -39

Combine like terms: 42 + -39 = 3
-1x = 3

Divide each side by '-1'.
x = -3

Simplifying
x = -3