Part 1
In this problem
the fractions have different denominators, which makes it difficult to compare
so
Find out an equivalent fraction for each student
2/3 ----> multiply by 4/4 ----> (2/3)*(4/4)=8/12
11/12
5/6 ---> multiply by 2/2 ----> (5/6)*(2/2)=10/12
7/12
Now, all the fractions have the same denominator
therefore
The fastest boy's time is 7/12
The slowest boy's time is 11/12
Find out the difference
(11/12)-(7/12)=5/12 minutes
The difference is 5/12 minutes
Part 2
The fastest boy's time is 7/12
7/12 < 2 7/12
that means
the boys broke the record
Find out the difference
2 7/12-7/12
Remember that
2 7/12=2+7/12
so
2+7/12-7/12=2 minutes
Is much faster by 2 minutes