1+4=5 2+5=12 3+6=24 5+8=? what's the answer

I have seen this problem before, except it was worded differently. Is this the problem you wished to express?

1+4=5, 2+5=12, 3+6=21, 8+11=?                                                                          

If so, then your answer is to simply add the last answer to the next problem. If not, then I am afraid I cannot help you.

1+4=5

5+2+5=12

12+3+6=21

21+8+11=40 

since there is 100 people this is easy since each person equals 1 5 so 56+19=75 . 75-100= 25 so 25% didn't order anything