Hello!
The answer is: 12.
Why?
Squaring means elevating the number by two, it means that the number will be mulitplied by itself two times. On the opposite, the square root of a number is the number that squared or elevated by two gives as result that number.
We must remember that:
![\sqrt[n]{a^(m) }=a^{(m)/(n) }\\\\√(a)=a^{(1)/(2)}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/v5jvmouvq70ha490d95rqbivhi7dr4lkff.png)
and,

Then, the square root of 12 square is:

Hence, the square root of 12 squared, is 12.
Have a nice day!