Answer
$-5;7$
Work Step by Step
$\ln \left( 3-x\right) +\ln \left( 5-x\right) =\ln \left( 50-6x\right) \Rightarrow \ln \left[ \left( 3-x\right) \left( 5-x\right) \right] =\ln \left( 50-60x\right) $
$\Rightarrow 15+x^{2}-8x=50-6x\Rightarrow x^{2}-2x-35=0$
$\Rightarrow x_{1},2=\dfrac {-b\pm \sqrt {b^{2}-4ac}}{2a}=\dfrac {2\pm \sqrt {2^{2}-4\times 1\times \left( -35\right) }}{2}=\dfrac {2\pm 12}{2}=-5;7$