Hi, 

Keiko bicycles 8km/h faster than Javier. 

Let x and (x+8) represent Javier's and Keiko's speeds respectively

Question states*** Note: D = rt or D/r = t

In the same time it takes Javier to bicycle 30 km, Keiko can bicycle 54 km.

  Cross Multiplying to solve

    54x = 30x + 240

      24x = 240

        x = 240/24 =10kmph, Javier's speed.  Keiko's speed is 18kmph 

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