$\begin{align}  & \text{Let the ages of Musa and Lawal be }x\text{ and }y \\ & x+y=28\text{ (sum of their ages)} \\ & \text{Total amount of money shared}=N600+N800=N1400 \\ & \text{Sharing Ratio} \\ & \frac{x}{28}\times 1400=600\text{     (Musa Share)} \\ & x=\frac{28\times 600}{1400}=12 \\ & \text{Musa }\!\!'\!\!\text{ s age }=12\text{ years old} \\ & \frac{y}{28}\times 1400=800\text{     (Lawal share)} \\ & y=\frac{800\times 28}{1400}=16 \\ & \text{Lawal }\!\!'\!\!\text{ s age }=16\text{ years old} \\\end{align}$