So, the equation would be 6*3x=36
First, divide by 6 on both sides!
Then you get 3x=6
Divide by 3 to isolate x, and you get x=2
X represents the missing side, so the missing side equals two!
To check your answer, plug 2 back in for x! 6*3*2=36
6*6=36
36=36
So that means your answer is right!
I hope this helps!