On average the number of electronic keyboards sold in Michigan each year is 39,720, which is five times the average number of electronic keyboards sold each year in Montana. How many electronic keyboards, on average, are sold each year in Montana?

Frank has a devised a formula for his catering business that calculates the number of meatballs he needs to prepare. the formula is m=4a+2c, where c=number of children; m=number of meatballs; a=number of adults. how many meatballs are required for a party of 10 adults and 5 children?