How to find A:B ?
 

A's age is 9.09% less than B's age.

How to find A:B from this above condition? Answer is 10/11

I tried:

9.09% = 1/11

B-A=1/11, so,

B=1/11+A,

=>

A/B = A/(1/11+A),

or

A/B=(B-1/11)/B,

or

A/B = (B-1/11)/(1/11+A).

If B's age is 100%, A's age is 9.09% less than B, so A's age is 90.91%
90.91:100 is close to 10:11