Answer:
5 3/4 hours
Explanation:
They drove 3 1/2 hours then 2 1/4 hours. We need to find the total of these to find how long this part of the trip was
(3 + 1/2) + (2 + 1/4) = 5 + 1/2 + 1/4
For 1/2, we can multiply both the numerator and denominator by 2 to get
1/2 = 2/4
Substituting that in, we get
5 + 2/4 + 1/4
= 5 + 3/4 hours