The first answer
-40y3/x5
So if there are twenty children and 6 have an average age of five, you could say their total age together is 30 years. The others (20-6) have an age of 8.
30+ (20-6)*8 = total age of every child at the library. From there divide by the number of children.
She has 2 minutes and 54 seconds left for question C.
20 minutes total
10 minutes and 42 seconds on question A
6 minutes and 24 seconds on question B
= 17 minutes and 6 seconds spent on both questions
20 minutes minus 17 minutes and 6 seconds = 2 minutes and 54 seconds
22 = 100%
26,40 = x%
26,4*100/22=120%
x=120%
120%-100%=20%
The answer is 20%