[tex]\displaystyle\bf\\\frac{y^{2} -25}{y^{2} +12y+36} \cdot\frac{3y+18}{2y+10} =\frac{(y-5)(y+5)}{(y+6)^{2} } \cdot\frac{3\cdot(y+6)}{2\cdot(y+5)} =\\\\\\=\frac{3\cdot(y-5)}{2\cdot(y+6)} \\\\\\y=-5\\\\\\\frac{3\cdot(y-5)}{2\cdot(y+6)} =\frac{3\cdot(-5-5)}{2\cdot(-5+6)} =\frac{3\cdot(-10)}{2} =-\frac{30}{2}=-15\\\\\\Otvet: \ -15[/tex]