Help! Difficult math question on SAT

20. Graham walked to school at an average speed of 3 miles an hour and jogged back the same route at 5 miles an hour. If his total traveling time was 1 hour, what was the total number of miles in the round trip?

A) 3
B) 3 1/8
C) 3 3/4
D) 4
E) 5

I don't know how to get the answer! (The answer is B by the way)

Distance = r * t
3(t1) = Dist to
5(t2) = Dist from
Didstances are equal
3(t1) = 5(t2)
t1+t2 = 1
t2= 1-t1
3(t1) = 5(1-t1)
3t1 = 5-5t1
8t1 = 5
t1 = 5/8
dist to = 3t1= 15/8
dist from = 5(3/8) = 15/8
Total = 30/8 = 3 3/4

You're sure its B???

This is a 3rd grade question.

And you are taking the SAT?

What grade are you in? 2nd? Isn't it a bit too early to take the SAT?