How can you subtract mixed numbers when the fractions in the first mixed number is less than the fraction in the second mixed number?

Two friends went to get ice cream sundaes. they each chose a flavor of ice cream from a list of vanilla and chocolate and toppings from a list of hot fudge, strawberries, sprinkles, peanuts, and whipped cream. use the sets below describing their choices and find b'. let a = {vanilla, chocolate, hot fudge, strawberries, sprinkles, peanuts, whipped cream} let b = {vanilla, hot fudge, sprinkles, whipped cream} let c = {chocolate, hot fudge, peanuts, whipped cream} {vanilla, hot fudge, sprinkles, whipped cream} {chocolate, strawberries, peanuts} {chocolate, strawberries} {vanilla, strawberries, peanuts}