Answer:
They drove 87.5% of the trip so far.
Step-by-step explanation:
The total of the trip is 100%.
On Monday, they drove 3/8 of the trip
So on Monday, 3/8 = 0.375.
On Tuesday they drove 4/8 of the trip
So on Tuesday, 4/8 = 0.5
How much of the trip did they drive so far?
0.375 + 0.5 = 0.875
They drove 87.5% of the trip so far.