14^2 + 10^2 -11^2/ 2*13*10

$$14^2 + 10^2 - \frac{11^2}{2\times{13}\times{10}}$$

$$196 + 100 -\frac{121}{260}$$

$$296 - \frac{121}{260} \approx 268.5346$$

Or if you meant:

$$14^2 + 10^2 -\frac{11^2\times{13}\times{10}}{2}$$

$$196 + 100 -({121\times{13}\times{5})$$

$$296 - 7865$$

$$-7569$$

By the order of operations,  zacismyname's  second answer is correct as  the problem is written.