\[\frac{2y - 7}{y^{2} - 9} - \frac{y - 10}{y^{2} - 9} =\]
\[= \frac{2y - 7 - y + 10}{y^{2} - 9} =\]
\[= \frac{y + 3}{(y + 3)(y - 3)} = \frac{1}{y - 3};\]
\[y = 3,1:\]
\[\frac{1}{3,1 - 3} = \frac{1}{0,1} = 10.\]