Answer:
x=5
Explanation:
We kind of have to work backward.
First, we take 12+3 because when we move it over the equal sign, we make it the opposite.
12+3=15
Our new equation is now, 3x=15
We now take:
3x__=15
The blank represents x, which is 5.
Hope this helps!
-AxekickNebulite