 <translate> Speed in down stream = 10 +8 = 18
Time taken to cover 90 km down stream = 90/18 = 5 hrs.
The final answer: (B). <yor> Iyara ní ìsàlẹ̀ odò = 10 + 8 = 18 Akoko ti o gba lati bo 90 km ni isalẹ odo = 90/18 = wakati marun. Ìdáhùn tó péye: (B). 