Verified Answer :

I think it is 6 and 16 but I could be wrong. Wait for more answers

There is anĀ infinite number of equivalent ratios for 21:56, but easierĀ ones are:

42:112 (because 21 2 = 42 and 56 2 = 112)
63:168 (because 21 3 = 63 and 56 3 = 168)
84:224 (because 21 4 = 84 and 56 4 = 224)