\( \Large V_{1} + V_{2} = \frac{15}{3\frac{3}{4}} \) = 4 km/hr  ... (1)

\( \Large V_{1} - V_{2} = \frac{5}{2\frac{1}{2}} \) = 2 km/hr ... (2)

Solving eqations (i) and (ii), we get

\( \Large v_{1} = 3 km/hr \) and \( \Large v_{2} = 1 km/hr \)