Question 1037887
John loads 1/20 of his truck per hour.  Peter takes 3X as long, or 1/60 trucks per hour. So:
1/20+1/60=Amount they can fill per hour
3/60+1/60=4/60=1/15
Since they fill 1/15 truck per hour, it will take them 15 hours together to fill the truck!!!!!!!!!!!