S = ut + 1/2 at^2
u = 10 a= -2 t= 1/2

work out the value of s .

s =

when it is a=ut+½a(t)²

s=(10×½)+½(-2×½²)

s=5+(-1×¼)

s=5-¼

s=4.25

since the airplane is moving with constant speed then the distance travelled can be calculated by x=u*t

in km/h would be:

x=640*3.5=2.240 km

in m/s would be:

u=640 km/h= 640.000 m/h =640.000/ 3600 m/s =177.8 m/s

t= 3.5 h= 3.5 * 3600 s=12.600 s

then x=u*t= 177.8*12.600= 2.240.280 m

the answer is 45 i just did it on oddesy ware