3a+2(a+6)=42

Solution for 3a+2(a+6)=42 equation:

Simplifying
3a + 2(a + 6) = 42

Reorder the terms:
3a + 2(6 + a) = 42
3a + (6 * 2 + a * 2) = 42
3a + (12 + 2a) = 42

Reorder the terms:
12 + 3a + 2a = 42

Combine like terms: 3a + 2a = 5a
12 + 5a = 42

Solving
12 + 5a = 42

Solving for variable 'a'.

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

Add '-12' to each side of the equation.
12 + -12 + 5a = 42 + -12

Combine like terms: 12 + -12 = 0
0 + 5a = 42 + -12
5a = 42 + -12

Combine like terms: 42 + -12 = 30
5a = 30

Divide each side by '5'.
a = 6

Simplifying
a = 6