distance = speed * time

let 't' represent the time in hours flown by the jet, then 't+2' represents the hours flown by the propeller plane

let 'v' represent the speed of the propeller plane, then 'v+75'' represents the speed of the jet

4500 = t(v+75)

4500 = (t+2)v, so v= 4500/(t+2)

substituting 'v' with '4500/(t+2)' in the first equation gives:

4500 = t((4500/(t+2)) + 75)

solving for 't' gives a positive value of t=10

substituting '10' for 't' gives:

4500 = 10(v+75)

solving for 'v' gives v=375

375+75 = 450

the propeller plane flies 375 mph, the jet flies 450 mph