So, we need 10 1/2 yards of fabric, and we have 2 1/2 + 4 1/2 years of fabric. We can subtract what we have from what we need, to find how much more we are missing.
First, let's convert these numbers into proper fractions.
10 1/2 = 20/2 + 1/2 = 21/2
2 1/2 = 4/2 + 1/2 = 5/2
4 1/2 = 8/2 + 1/2 = 9/2
So the equation we need to solve is,
21/2 - 5/2 - 9/2 =
Subtracting, we find
21/2 - 5/2 - 9/2 = 7/2
Now we can convert back to an improper fraction,
7/2 = 6/2 + 1/2 = 3 1/2
So we need 3 1/2 more yards of fabric.