One more thing just to add a little smoke and mirrors...
The Time signature can be thought of as a fraction, which equals one measure. The fraction doesn't have to equal one, but it equals one measure.
12/8 says 12 eighth notes = 1 measure.
Just like math taught us (or tried to teach us), If the numerator and demomimator are both divisible by a common prime number, then:
12/8 = 6/4 6 quarter notes = 1 measure.
12/8 = 3/2 3 half notes = 1 measure.
Obviously, you can mix and match different length notes to achieve a measure, but that's what will test your math skills.
4/4 timing spoils us all, since that's essentially what western music most commonly uses, which is why a letter "C" often appears instead of a time signature, indicating Common timing.
4/4 4 quarter notes =1 measure
2/2 2 half notes = 1 measure
1/1 1 whole note = 1 measure
I'll stop now. My brain is starting to hurt.