Question 578746
Write it out as a system of 2 equations:

t1 = time driving 100 km/h
t2 = time driving 80 km/h

t1 + t2 = 5.5 

100t1 + 80t2 = 500

*[invoke linear "x", "y", 1, 1, 5.5, 100, 80, 500 ]

t1 = 3 hrs
t2 = 2.5 hrs

CHECK:

3 + 2.5 = 5.5 √

100(3) + 80(2.5) = 300 + 200 = 500 km √