Amount of pizza dough that Rosa has = 4 1/2 pounds = 9/2 pounds Amount of dough required by Rosa to make 1 pizza = 3/4 pounds Then The number of pizza that can be made with 9/2 pounds of dough = 1/(3/4) * (9/2) = (4/3) * (9/2) = 2 * 3 = 6 So Rosa can make 6 pizzas with the amount of dough she has.
I hope the procedure is clear enough for you to understand.
Glad to have helped you.