A container holds a mixture of liquid A and liquid B in the ratio 7:5. After 9 litres of this mixture are removed and the container is refilled with pure liquid B, the proportion of A to B changes to 7:9. Determine the initial quantity of liquid A present in the container.

A shopkeeper mixes two types of rice in the ratio 5 : 3, where one type costs ₹75 per kg and the other costs ₹85 per kg. Find the average price per kg of the mixture.

In what ratio (cheaper to dearer) should a grocer mix two varieties of pulses costing ₹18 and ₹22 per kg, respectively, to obtain a mixture worth ₹19.50 per kg?