so a plane is going 680 north then encounters wind blowing east at 75 miles. So the resultant will be something north east but closer to north since going north is more than 8x faster based on velocity than 75 miles.
so in still air x=680
so using pythagorean theorem is 680^2+75^2= c^2 and once you solve you get 684.1235mph
this question involves vectors and using the pythagorean theorem