UPSC CDS II 2024 Math Paper

There are two containers A and B. In container A, the ratio of milk and water is 1 : 3 and in container B, the ratio of milk and water is m : n. If the mixture in the containers A and B are mixed in the ratio 2 : 3 to get 20 litres of a mixture having milk and water in the ratio 3 : 7, then what is the value of (m)/(n)?