If 5 men or 7 women can earn Rs. 5250 per day, how much would 7 men and 13 women earn per day ?

Answer: Option D

Let the required earning be Rs. x
5 men = 7 women
7 men = $$\left(\frac{7}{5}\times 7\right)$$   women = $$\frac{49}{5}$$ women
∴ (7 men and 13 women)
$$\begin{array}{rl}& =\left(\frac{49}{5}+13\right)\text{women}\\ & =\frac{114}{5}\text{ women}\end{array}$$
Now, More women, More earning (Direct proportion)
$$\begin{array}{rl}& \therefore 7:\frac{114}{5}::\text{ 5}250:x\\ & \iff 7x=\left(\frac{114}{5}\times 5250\right)\\ & \iff 7x=119700\\ & \iff x=17100\end{array}$$