A person traveling 210 km by car drove the first part at 100

A person traveling 210 km by car drove the first part at 100 km/h and the rest at 80 km/h. If the trip took 2 (1/4) h to complete, what distance was traveled at 100 km/h?

Solution

rt+rt=d
100t+80(2.25-t)=210
t=1.5 hr. at 100kph
2.25-1.5=.75 hr at 80 kpm