so the speeds are s and s+40
distance=speed times time
if we assume the time is the same, and it is t
350=(s+40)(t)
and
150=(s)(t)
so
350=st+40t
150=st
multiply 2nd equation by -1 and add to first
350=st+40t
-150=-st +
200=+0st=40t
200=40t
divide both sides by 40
5=t
so
speed=disatnce/time
s=150/5
s=30
slower car is 30mph
