Math assignment = 3/8 hours
History assignment = 1/4 hours
We can not compare this as both fractions do not have alike denominators.
We can fix this problem easily by turning 3/8 and 1/4 into alike denominator fractions.
We can turn 1/4 into 2/8 as it is equivalent fractions.
1 x 2 = 2
4 x 2 = 8
(Whatever you do to the denominator, you have to do the same to the numerator)
Once we get this, we can see that Shen spent 2/8 hours on his homework while he spent 3/8 hours on his math assignment.
3/8 - 2/8 = 1/8
1/8 = 0.125
Shen spent 1/8 of an hour (or 0.125 of an hour) more on his math assignment than his history assignment.