-6a+3+7a=16-21

Solution for -6a+3+7a=16-21 equation:

Simplifying
-6a + 3 + 7a = 16 + -21

Reorder the terms:
3 + -6a + 7a = 16 + -21

Combine like terms: -6a + 7a = 1a
3 + 1a = 16 + -21

Combine like terms: 16 + -21 = -5
3 + 1a = -5

Solving
3 + 1a = -5

Solving for variable 'a'.

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

Add '-3' to each side of the equation.
3 + -3 + 1a = -5 + -3

Combine like terms: 3 + -3 = 0
0 + 1a = -5 + -3
1a = -5 + -3

Combine like terms: -5 + -3 = -8
1a = -8

Divide each side by '1'.
a = -8

Simplifying
a = -8