To simply ratios, we need to get the common factor of the ratio, and divide the ratio by this common factor.
For a) 33 : 121
33 = 3 x 11
121 = 11 x 11
So the common factor of this ratio is 11
Dividing the ratio by 11 :
The answer is 3 : 11
For b) 30 : 72
30 = 2 x 3 x 5
72 = 2 x 2 x 2 x 3 x 3
So the common factor of this ratio is 2 x 3 = 6
Dividing the ratio by 6 :
The answer is 5 : 12