What coins?
Latha bought a pencil and a pen for seven and a half rupees. She gave Rs 10/−. The shopkeeper gave back the money in half and quarter rupees. What are the coins she got?

Cost of a pen and a pencil = Rs $7\frac{1}{2}$

Total money given to the shopkeeper = Rs 10

Total money returned to Latha by the shopkeeper = Rs 10 − Rs $7\frac{1}{2}$
                                                                                 $$\begin{gathered} =10-7-\frac{1}{2} \\ =3-\frac{1}{2} \\ =\mathrm{Rs} 2\frac{1}{2} \end{gathered}$$
  
We know that,
1 quarter rupee = 25 paise
1 half rupee       = 50 paise

Now, the shopkeeper can return Rs $2\frac{1}{2}$ in the following ways :
a) 1 half rupee coin and 8 quarter rupee coins

b) 4 half rupee coins and 2 quarter rupee coins

c) 2 half rupee coins and 6 quarter rupee coins

d) 3 half rupee coins and 4 quarter rupee coins