For a recipe, there are 3 eggs needed for every pound of cake needed. How many pounds of cake can be made if there are 40 eggs?

Write a proportion to represent the situation: \(\frac{\mathrm{3eggs} }{\mathrm{1cake}} = \frac{\mathrm{ 40eggs} }{\mathrm{xcakes}}\)
Cross multiply and solve for the variable x: \(3x=40 \rightarrow x= 13\frac{\mathrm{1} }{\mathrm{3}} \)
Only 13 pounds of cake can be made.