So for this problem you first need to distribute and it should become easier from there.
3(x - 3) = 0
Distribute.
3x - 9 = 0
Isolate the variable by adding 9 to both sides.
3x = 9
Divide.
x = 3
So now lets check our work.
3( x - 3) = 0
3( 3 - 3) = 0
9 - 9 = 0
0 = 0
It is correct so 3 is your answer. I hope this helps love! :)