Find the missing value for problem 15, given the pattern (Bottom Left) - (Bottom Right) = Top, and the values Top = 2 1/4 and Bottom Right = 10 3/4.

The top number is $2\frac{1}{4}$.
The bottom right number is $10\frac{3}{4}$.
Let the missing bottom left number be $X$.

(Bottom Left) - (Bottom Right) = Top.

Add the whole numbers: $2 + 10 = 12$.
Add the fractions: $\frac{1}{4} + \frac{3}{4} = \frac{1+3}{4} = \frac{4}{4}$.

The fraction $\frac{4}{4}$ is equal to 1.
So, $X = 12 + 1 = 13$.

The missing value for is $\boxed{\text{13}}$.