6a^2+3a^2+18-30=15

Solution for 6a^2+3a^2+18-30=15 equation:

Simplifying
6a2 + 3a2 + 18 + -30 = 15

Reorder the terms:
18 + -30 + 6a2 + 3a2 = 15

Combine like terms: 18 + -30 = -12
-12 + 6a2 + 3a2 = 15

Combine like terms: 6a2 + 3a2 = 9a2
-12 + 9a2 = 15

Solving
-12 + 9a2 = 15

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 + 9a2 = 15 + 12

Combine like terms: -12 + 12 = 0
0 + 9a2 = 15 + 12
9a2 = 15 + 12

Combine like terms: 15 + 12 = 27
9a2 = 27

Divide each side by '9'.
a2 = 3

Simplifying
a2 = 3

Take the square root of each side:
a = {-1.732050808, 1.732050808}