You've got something wrong. It's too easy. The answer is immediately 12.
Look what you wrote and notice the words in rede:
ABCD is a trapezoid. E is the midpoint of CD,
and F is the midpoint of AB. If CD is 24, what is the
length of CE? AD=16, and EF=12. How would i calculate the answer?
Now let's just look only at your red words, nothing else:
E is the midpoint of CD
CD is 24, what is the length of CE?

See? You can forget the trapezoid and all the other letters and numbers.
Obviously if E is the midpoint of CD, and CD is 24, CE is going to be
half of CD, or 12.
That COULDN'T possibly have been what you were asked.
Either fix it and repost, or tell me what it should be in the thank-you
note below.
Edwin