I need help with this question

Question

kevin walks and jogs to his favorite coffee shop to study each weekend. He averages 4 mph walking and 5 mph jogging. The distance from his home to the coffee shop is 17 mi, and he makes the trip in 4 hr. How long does Kevin jog?

 

Answer 1

d=r*t

17=4t+5(4-t)

17=4t+20-5t

17=-t+20

t=20-17

t=3 hours walking and 4-t=4-3=1 hour jogging

17=4*3+5*1=12+5=17