2. The excursion boat Holiday travels 35km upstream and then back again in 4h 48min. If the speed of the Holiday in still water is 15km/h, what is the speed of the current?

Answer 1

speed of current ---- x km/h

speed against current --- 15-x
speed with current ----- 15+x

time against current = 35/(15-x)
time with current = 35/(15+x)

so solve
35/(15-x) + 35/(15+x) = 4.8

(I suggest multiplying each term by (5+x)(15-x), you will end up with a quadratic equation )