2[s+3(a-1)]=18

Solution for 2[s+3(a-1)]=18 equation:

Simplifying
2[s + 3(a + -1)] = 18

Reorder the terms:
2[s + 3(-1 + a)] = 18
2[s + (-1 * 3 + a * 3)] = 18
2[s + (-3 + 3a)] = 18

Reorder the terms:
2[-3 + 3a + s] = 18
[-3 * 2 + 3a * 2 + s * 2] = 18
[-6 + 6a + 2s] = 18

Solving
-6 + 6a + 2s = 18

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 + 6a + 6 + 2s = 18 + 6

Reorder the terms:
-6 + 6 + 6a + 2s = 18 + 6

Combine like terms: -6 + 6 = 0
0 + 6a + 2s = 18 + 6
6a + 2s = 18 + 6

Combine like terms: 18 + 6 = 24
6a + 2s = 24

Add '-2s' to each side of the equation.
6a + 2s + -2s = 24 + -2s

Combine like terms: 2s + -2s = 0
6a + 0 = 24 + -2s
6a = 24 + -2s

Divide each side by '6'.
a = 4 + -0.3333333333s

Simplifying
a = 4 + -0.3333333333s