Total number of black marbles = 24
Total number of blue marbles = 12
The ratio of black marbles to blue marbles​ means we are to divide the black marbles by the blue marbles as shown:
Black : Blue = 24 : 12
Black/Blue = 24/12
Black/blue = 2
Hence the ratio of black marbles to blue marbles is 2.
Option A is also correct since black/blue = 24/12
The two correct options are A and C
