Answer:
x = 13
Step-by-step explanation:
-6+12+3x=45
6+3x=45
6+3x-6=45-6
3x=39
x=13
-6 + 3x + 12 = 45
-6 + 12 + 3x = 45
6+3x = 45
-6 -6
3x = 39
/3 /3
Hope this helps :)