Find the ratio compounded of the duplicate ratio of 5 : 6, the reciprocal ratio of 25 : 42 and the sub-duplicate ratio of 36 : 49.

Find the value of x, if (3x - 7) : (4x + 3) is the sub-triplicate ratio of 8 : 27

What quantity must be added to each term of the ratio x : y so that it may become equal to c : d ?