To solve the problem we will use this equation where,
d will be distance.
x is the speed of the plane without tailwind.
y is the speed of the wind affecting the plane.
Going to Philadelphia the speed of the plane affected by wind will be x-y=220 miles/hr
Coming back with a tailwind, the speed of the plane will be x+y= 280 miles/hr.
since time = distance / speed, t1 =d/220 and t2 = d/280
and since the total time traveled is 6.5hrs
d/220 + d/ 280 = 6.5hrs
d = 800.8 miles x 2 (back and forth trip) the answer is 1601.6 miles