$\frac{-7}{25}$ . $\frac{11}{13}$ + $\frac{-7}{25}$ . $\frac{2}{13}$ - $\frac{18}{25}$
= ( $\frac{-7}{25}$ . $\frac{11}{13}$ - $\frac{7}{25}$ . $\frac{2}{13}$ ) - $\frac{18}{25}$
= $\frac{-7}{25}$ . ($\frac{11}{13}$ + $\frac{2}{13}$ ) - $\frac{18}{25}$
= $\frac{-7}{25}$ . 1 - $\frac{18}{25}$
= $\frac{-7}{25}$ - $\frac{18}{25}$
= -1