Kathy starts with a number she adds 3 touring numbers then doubles the results finally she subtract 7 if she ended with nine what number did she start with

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?