From the two statements we can say:
260=(215+w)t
t=260/(215+w)
Now from the second statement:
170=(215-w)t
t=170/(215-w)
We are told that t=t, for the downwind and upwind equations so:
260/(215+w)=170/(215-w)
260(215-w)=170(215+w)
55900-260w=36550+170w
-430w=-19350
w=45
So the wind speed is 45mph.