a+(a+2)+(a+4)=-42

Solution for a+(a+2)+(a+4)=-42 equation:

Simplifying
a + (a + 2) + (a + 4) = -42

Reorder the terms:
a + (2 + a) + (a + 4) = -42

Remove parenthesis around (2 + a)
a + 2 + a + (a + 4) = -42

Reorder the terms:
a + 2 + a + (4 + a) = -42

Remove parenthesis around (4 + a)
a + 2 + a + 4 + a = -42

Reorder the terms:
2 + 4 + a + a + a = -42

Combine like terms: 2 + 4 = 6
6 + a + a + a = -42

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

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

Solving
6 + 3a = -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 + 3a = -42 + -6

Combine like terms: 6 + -6 = 0
0 + 3a = -42 + -6
3a = -42 + -6

Combine like terms: -42 + -6 = -48
3a = -48

Divide each side by '3'.
a = -16

Simplifying
a = -16