Step-by-step explanation:
the slower plane traveled x miles in 4 hours.
the faster plane traveled x + 4×80 = x + 320 miles in 4 hours.
so,
x + x + 320 = 3800 miles
2x =3480 miles
x =1740 miles (in 4 hours) .
that means the slower plane's speed was 435 mph.
and the faster plane's speed was 435 + 80 = 515 mph.