Beth had made 12 cupcakes. this is 30% of the cupcakes she must make. how many cupcakes must she make?

What we know:
12 cupcakes already made
12 is 30% of total cupcakes (c) needed
Total cupcakes c are 100%

What we need to find:
Total cup cakes c

Set up propportion:

12/30=c/100
30c=(12)(100)
30c=1200
30/30c=1200/30
c=40
She needs to make a total of 40 cupcakes.