Hmm.. they each drove 90 miles, and neither person did more driving than the other.
It is a round trip, therefore the distance between destinations are equal.
Jack's 40 miles + Jill's A miles = Jack's B miles + Jill's 50 miles
A + B = 40 miles + 50 miles
Solving, A = 50 and B = 40
Is that right, Lisa?