1. We assume, that the number 96 is 100% - because it's the output value of the task.
2. We assume, that x is the value we are looking for.
3. If 96 is 100%, so we can write it down as 96=100%.
4. We know, that x is 33% of the output value, so we can write it down as x=33%.
5. Now we have two simple equations:
1) 96=100%
2) x=33%
where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that:
96/x=100%/33%