What is the irrational number in this set: 12.89, square root of 12 and 12/144 ?

Good night, 

Irrational numbers are those that can't be expressed as a fraction:

12.89 can be expressed as: 



The above numbers can be expressed as a fraction, then the logical answer is: 

But we will check the  



As you can see we can't express that number as a fraction, so that is te correct answer.