Here is an example of a filled in spreadsheet. I'll be using a pattern for a pullover collared shirt. I also have these three main fabrics that all go well with blue thread, so I can sew them all at the same time without changing thread. I need to make a size 5 and 7 anyway, but I thought I'd see what other sizes I could squeeze in. You'll notice in cell X5 I have a negative value for my blue solid fabric that goes with the whale main fabric. However, this is the same as the two other blue solid fabrics above it, so in reality I'll have 8+21-5 = 24" of the blue solid leftover if I make all these shirts.
For the purpose of this class I will only be making the shirts with the Airplanes and Whales in a size 5 and 7, so 4 shirts total.