3-(-12)=4a-a

Solution for 3-(-12)=4a-a equation:

Simplifying
3 + -1(-12) = 4a + -1a

Multiply -1 * -12
3 + 12 = 4a + -1a

Combine like terms: 3 + 12 = 15
15 = 4a + -1a

Combine like terms: 4a + -1a = 3a
15 = 3a

Solving
15 = 3a

Solving for variable 'a'.

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

Add '-3a' to each side of the equation.
15 + -3a = 3a + -3a

Combine like terms: 3a + -3a = 0
15 + -3a = 0

Add '-15' to each side of the equation.
15 + -15 + -3a = 0 + -15

Combine like terms: 15 + -15 = 0
0 + -3a = 0 + -15
-3a = 0 + -15

Combine like terms: 0 + -15 = -15
-3a = -15

Divide each side by '-3'.
a = 5

Simplifying
a = 5