Let
x--------> Peter's drive speed on the highway in mph
y--------> Peter's drive speed on country roads in mph
we know that
x=25+y-------> equation 1
70/y=120/x------> 70*x=120*y-----> x=120*y/70------> equation 2
remember that
time=distance/speed
equate equation 1 and equation 2
25+y=120*y/70-----> multiply by 70 both sides
70*[25+y]=120*y-----> 1,750+70*y=120*y-----> 50*y=1,750------> y=35 mph
x=25+35------> x=60 mph
the answer is
Peter's drive speed on the highway is 60 mph
Peter's drive speed on country roads is 35 mph