a rower can row 7 km / h in still water . when the river is running at 1 km / h , it takes the rower 1 hour to row to big rock and back . how many kilometers is it to big rock ?
"let x be the distance to big rock . time = x / 6 + x / 8 = 1 x = 48 / 14 = 3.43 km the answer is d ."
multiply(divide(subtract(7, 1), add(add(7, 1), subtract(7, 1))), add(7, 1))