The amount that Sean borrowed at 7.5% per year, compounded annually, for which he paid $2,244.92 after three years is $1,807.07.
We can use the present value Formula:

PV = present value
FV = future value
r = rate of return
= number of periods
We can determine the present value using an online finance calculator as follows:
N (# of periods) = 3 years
I/Y (Interest per year) = 7.5%
PMT (Periodic Payment) = $0
FV (Future Value) = $2,244.92
Results:
PV (present value) = $1,807.07
Total Interest= $437.85