Keiko bicycles 6km/h faster than Carlos. In the same time it takes Carlos to bicycle 30km, Keiko can bicycle 48km. How fast does each bicyclist travel?

Let the speed of Carlos be x then speed of Keiko will be x+6

Equation will be

30/x = 48/(x+6)

30(x+6) = 48x

30x + 180 = 48x

180 = 18x

x = 10

Speed of Carlos: 10 km/h

Speed of Keiko: x + 6 = 16 km/h