Question 306483
D=RT
180=(R+20)T
T=180/(R+20)
120=RT
T=120/R
SET THE 2 T EQUATIONS EQUAL.
180/(R+20)=120/R CROSS MULTIPLY.
180R=120(R+20)
180R=120R+2,400
180R-120R=2,400
60R=2,400
R=2,400/60
R=40 mph. for the slower car.
40+20=60 mph. for the faster car.
Proof:
180/60=120/40
3=3 ans. for the travel time.