Final answer:
Using a proportion, where 7 iced cupcakes cost $21, it is determined that 5 iced cupcakes would cost $15 by setting up the proportion 7 cupcakes / $21 = 5 cupcakes / x dollars, cross-multiplying, and solving for x.
Step-by-step explanation:
To solve the question using a proportion, first we need to understand that a proportion is an equation that says that two ratios are equivalent. In this case, we are comparing the cost of iced cupcakes to the number of iced cupcakes.
Let's set up a proportion using the information that 7 iced cupcakes cost $21. We want to find out how much 5 iced cupcakes would cost. The proportion would look like this:
7 cupcakes / $21 = 5 cupcakes / x dollars
To solve for x, we cross-multiply and then divide:
(7 cupcakes) * (x dollars) = (5 cupcakes) * ($21)
7x = 105
Then divide both sides by 7 to solve for x:
x = 105 / 7
x = $15
Therefore, 5 iced cupcakes would cost $15.