Whats the answer to -12(4/3-1)

Which strategy is used by public health to reduce the incidence of food poisoning?

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?

Pls the last one and it has to be like number 6