It would help if you proofread your questions before you posted them (27km/h).
Robert's speed = x and Elena's = x + 4
time = distance/rate
27/x = 39/(x+4)
Solve for x, then x+4.
Elena bicycles 4 km/h faster than Robert. In the same time it takes Robert to bicycle 27km/h, Elena can bicycle 39 km. How fast does each bicycle travel?
1 answer