a boat goes 100 km downstream in 10 hours , and 60 m upstream in 15 hours . the speed of the stream is ?
"100 - - - 10 ds = 10 ? - - - - 1 60 - - - - 15 us = 4 ? - - - - - 1 s = ( 10 - 4 ) / 2 = 3 kmp answer : a"
divide(subtract(divide(100, 10), divide(60, 15)), const_2)