Final answer:
The question is about using algebra to determine the prices of individual items ordered by families at a pizza restaurant based on their total bills. The given equation and the additional information provided are not sufficient to solve for the unit prices without more details. A separate demand equation for pizzas is provided but is not directly related to solving the original problem.
Step-by-step explanation:
The Pizza Shack problem presents a mathematics scenario in the context of buying pizzas and soft drinks, and relates to creating equations from word problems and solving for unknowns in algebra. The given equation, 5C + 3T + 12D = 61.50, likely represents the total cost of the Washington family's order with C representing the cost of each cheese pizza, T the additional toppings, and D the cost of each soft drink. However, the equation itself is incomplete without further information or additional equations from the Divitas' and Lees' orders to form a system of equations to solve for the individual prices of C, T, and D.
To solve the problem based on just the equations for the Washington family, we would need the individual costs of the items. The calculation provided about pizza demand, Qd = 16 - 2P, where P is the price, seems to be from a different context related to economics and does not directly help in solving the given problem about The Pizza Shack. Nonetheless, when applying this unrelated equation, if the price of each personal pizza (P) is $2, then consumers will buy Qd = 16 - 2(2) = 12 personal pizzas. This demonstrates how to use a basic demand equation, indicating that the quantity demanded (Qd) varies inversely with the price (P).