Answer:
1. The quotient in simplest form is 4
2. It take him 8 minutes to run 1 mile.
Step-by-step explanation:
Given:
9 divided by 2 1/4.
Sean runs 3 1/2 miles in 28 minutes.
Now, to find the quotient in simplest form and the time it takes Sean to run 1 mile.
1. 9 divided by 2 1/4.

Converting mixed fraction into improper:
= 
Converting 9/4 into decimal:
= 
= 
Therefore, the quotient in simplest form is 4.
2. Sean runs 3 1/2 miles in 28 minutes.
Sean runs 7/2 miles in 28 minutes.
Now, solving it by unitary method:
Sean runs 7/2 miles in 28 minutes.
Sean runs 1 mile in =
.
= 
= 
Therefore, it take him 8 minutes to run 1 mile.