[tex]a) \frac{x+3}{x-1}= \frac{9}{7}\Rightarrow 7x+21=9x-9\Rightarrow 21+9=9x-7x\Rightarrow \boxed{x=15} \\ b) \frac{4}{ x^{2}-2 }= \frac{2}{7}\Rightarrow 28=2 x^{2} -4\Rightarrow2 x^{2}=32\Rightarrow \boxed{x=4} \\ c) \frac{2}{ x^{3} }= \frac{1}{4}\Rightarrow x^{3}=8\Rightarrow \boxed{x=2}[/tex]
