so 1 mile per 3 minute or
1 times 20=20
3 times 20=60
20 miles in 60 minutes or
20 miles per hour
20 mph with wind
4 mins agains the wind
multiply 15
15 miles per hour agains the wind
so d=st
distances are the same
d=st
20mph with the wind
20=wind+real speed
15mph agains the wind
15=real speed-wind
20=w+rs
15=-w+rs
add together
35=2(rs)
divide 2
real speed=17.5
