SHE SPENT 15 MINUTES MORE. 1 hour is 60 minutes. 1/2 hour is 30 minutes and 1/4 hour is 15 minutes. 30-15=15
For this case we must resolve the following expression:
We have to:

The base change rule can be used if a and b are greater than 1 and are not equal to x.
We substitute the values in the base change formula, using 

Answer:
-4
Option A
♥ Solve:
31/100
50/100
50 is larger than 31
Therefore 5/10 is larger than 31/100