a+a+7+3a+a-1=42

Solution for a+a+7+3a+a-1=42 equation:

Simplifying
a + a + 7 + 3a + a + -1 = 42

Reorder the terms:
7 + -1 + a + a + 3a + a = 42

Combine like terms: 7 + -1 = 6
6 + a + a + 3a + a = 42

Combine like terms: a + a = 2a
6 + 2a + 3a + a = 42

Combine like terms: 2a + 3a = 5a
6 + 5a + a = 42

Combine like terms: 5a + a = 6a
6 + 6a = 42

Solving
6 + 6a = 42

Solving for variable 'a'.

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

Add '-6' to each side of the equation.
6 + -6 + 6a = 42 + -6

Combine like terms: 6 + -6 = 0
0 + 6a = 42 + -6
6a = 42 + -6

Combine like terms: 42 + -6 = 36
6a = 36

Divide each side by '6'.
a = 6

Simplifying
a = 6