81-42=n

Solution for 81-42=n equation:

Simplifying
81 + -42 = n

Combine like terms: 81 + -42 = 39
39 = n

Solving
39 = n

Solving for variable 'n'.

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

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

Combine like terms: n + -1n = 0
39 + -1n = 0

Add '-39' to each side of the equation.
39 + -39 + -1n = 0 + -39

Combine like terms: 39 + -39 = 0
0 + -1n = 0 + -39
-1n = 0 + -39

Combine like terms: 0 + -39 = -39
-1n = -39

Divide each side by '-1'.
n = 39

Simplifying
n = 39