**Solution:**

Let the fixed charge for first three days and each day charge thereafter be Rs x and Rs y respectively.

According to the question,

x + 4y = 27 ... (i)

x + 2y = 21 ... (ii)

Subtracting equation (ii) from equation (i), we get

2y = 6

y = 3 ... (iii)

Putting in equation (i), we get

x + 12 =27

x = 15

Hence, **fixed charge = Rs 15 and Charge per day = Rs 3.**