42=8a+13a

Solution for 42=8a+13a equation:

Simplifying
42 = 8a + 13a

Combine like terms: 8a + 13a = 21a
42 = 21a

Solving
42 = 21a

Solving for variable 'a'.

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

Add '-21a' to each side of the equation.
42 + -21a = 21a + -21a

Combine like terms: 21a + -21a = 0
42 + -21a = 0

Add '-42' to each side of the equation.
42 + -42 + -21a = 0 + -42

Combine like terms: 42 + -42 = 0
0 + -21a = 0 + -42
-21a = 0 + -42

Combine like terms: 0 + -42 = -42
-21a = -42

Divide each side by '-21'.
a = 2

Simplifying
a = 2