Answer:
6
Step-by-step explanation:
The main idea of how to solve it is to isolate the variable. Whatever you multiply, divide, add, or subtract on one side, you must do the same to the other side so that both sides are equal.
3(x-1) = 21
3(x-1) / 3 = 21 / 3
x - 1 = 7
+ 1 + 1
x = 6
