-7(3-a)-a=13

Solution for -7(3-a)-a=13 equation:

Simplifying
-7(3 + -1a) + -1a = 13
(3 * -7 + -1a * -7) + -1a = 13
(-21 + 7a) + -1a = 13

Combine like terms: 7a + -1a = 6a
-21 + 6a = 13

Solving
-21 + 6a = 13

Solving for variable 'a'.

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

Add '21' to each side of the equation.
-21 + 21 + 6a = 13 + 21

Combine like terms: -21 + 21 = 0
0 + 6a = 13 + 21
6a = 13 + 21

Combine like terms: 13 + 21 = 34
6a = 34

Divide each side by '6'.
a = 5.666666667

Simplifying
a = 5.666666667