An airplane travels
2688km
against the wind in
4
hours and
3208km
with the wind in the same amount of time. what is the rate of the plane in still air and what is the rate of the wind?

Velocity (against wind) = 2,688 km / 4 hr = 672 km/hr
Velocity (with wind) = 3,208 km / 4 hr = 802 km/hr
psa means plane velocity in still air
ws means wind speed
psa -ws = 672
psa +ws = 802  We add both equations and get
2 psa = 1,474
plane velocity (in still air) = 737 km/hr

psa +ws = 802 so that means

wind speed = 802 -737 = 65 km/hr

Source:
http://www.1728.org/veloccal.htm
(My website)

60 ÷ -20 x makes x = -3

than do 23.50 times 18 and then divide your answer by 100 than you will get x.