Hey there! :D
First, convert 10 1/2 to a fraction with 4.
[tex] \frac{1}{2} = \frac{2}{4} [/tex]
[tex]10 \frac{2}{4} + 15 \frac{3}{4} = 26 \frac{1}{4} [/tex]
The fraction is already in its simplest form, so you don't have to change it.
I hope this helps!
~kaikers