[tex]\it a)\ \dfrac{3}{7}\ din\ \dfrac{25}{39}=\dfrac{3}{7}\cdot\dfrac{25}{39}=\dfrac{\ 75^{(3}}{273}=\dfrac{25}{91}\\ \\ \\ b)\ \dfrac{3}{7}\ din\ x = \dfrac{25}{39} \Rightarrow \dfrac{3}{7}\cdot x=\dfrac{25}{39} \Rightarrow x=\dfrac{25}{39}\cdot\dfrac{7}{3}=\dfrac{175}{117}[/tex]
