So you know distance=rate(time). You could use the equation 40(x)+20(2-x)=54. After simplifying, you get x=7/10 or 0.7 hrs. Btw, x represents time downhill, while 2-x represents time on flat terrain since the total is 2. If you don't want to read all that, the answer is 0.7 hrs.
Answer: 55 cookies in 80 mins Step-by-step explanation: 1 hour has 60 mins so 25/60=0.417 0.417/3=0.139 0.139x4=0.556 so he can eat 55 cookies in 80 mins