If 3 Big Mac sandwich combos cost $16.50 and the average number of Big Mac sandwich combos sold at a MacDonald restaurant each day is 500, then what is the average amount spent on Big Macs sandwich combos at a restaurant each day?

Megan and desmond each add the same amount of water to their aquarium megan makes 5 ml of chemical solution with every gallon of water for her aquarium desmond mixed 8 ml of chemical solution for every 2 gallon of the water for his aquarium.