how do i solve this word problem step by step

Question

Julie and Eric row their boat (at a constant speed) 40 miles downstream for 4 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 10 hours. Find the rate of the current.

Answer 1

distance = rate of speed times time

d=rt

40 = (b+c)4 = (b-c)10 where b = boat speed in still water, and c=current speed

10b-10c = 40 divide by 10

b - c = 4

4b +4c = 40 divide by 4

b + c = 10

add

2b =14

b = 7 = boat speed in still water

c = 10-7 =3 mph = current speed

40 =(7+3)4

40 =(7-3)10