-15-(-86)=a

Solution for -15-(-86)=a equation:

Simplifying
-15 + -1(-86) = a

Multiply -1 * -86
-15 + 86 = a

Combine like terms: -15 + 86 = 71
71 = a

Solving
71 = a

Solving for variable 'a'.

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

Add '-1a' to each side of the equation.
71 + -1a = a + -1a

Combine like terms: a + -1a = 0
71 + -1a = 0

Add '-71' to each side of the equation.
71 + -71 + -1a = 0 + -71

Combine like terms: 71 + -71 = 0
0 + -1a = 0 + -71
-1a = 0 + -71

Combine like terms: 0 + -71 = -71
-1a = -71

Divide each side by '-1'.
a = 71

Simplifying
a = 71