The Rivera family and the Cook family each used their sprinklers last summer. The water output rate for the Rivera family's sprinkler was 40 per hour. The water output rate for the Cook family's sprinkler was20 per hour. The families used their sprinklers for a combined total of 65 hours, resulting in a total water output of 2000. How long was each sprinkler used?

You coordinate volunteers for litter cleanup in local parks. your spreadsheet lists drivers and the number of seat belts in each driver’s car. the spreadsheet calculates the number of drivers (d) and the total number of seat belts (s). you want to know the maximum number of volunteers, besides drivers, that can be transported to the park in a single trip given that each person must have a seat belt of their own.