If x : y = 7 : 3, then the value of $$\frac{{xy + {y^2}}}{{{x^2} - {y^2}}}$$   is

$$\eqalign{ & = \frac{x}{y} = \frac{7}{3} \cr & = \frac{{xy + {y^2}}}{{{x^2} - {y^2}}} \cr & = \frac{{\left( {\frac{x}{y}} \right) + 1}}{{\left( {\frac{{{x^2}}}{{{y^2}}}} \right) - 1}} \cr & = \frac{{\frac{7}{3} + 1}}{{{{\left( {\frac{7}{3}} \right)}^2} - 1}} \cr & = \frac{{10}}{3} \times \frac{9}{{40}} \cr & = \frac{3}{4} \cr} $$