In order to solve this, start by distributing the 3.
Essentially, we multiplying each value inside the parenthesis by 3, to get:
3x + 12 = 3
Next, subtract 12 on both sides:
3x + 12 - 12 = 3 - 12
12 - 12 = 0
3 - 12 = -9
So:
3x = -9
The last step here is to divide both sides by 3:
3x ÷ 3 = -9 ÷ 3
3 • X ÷ 3 = X
-9 ÷ 3 = -3
So, long story short, X = -3