There is no direct square root of 24, however the decimal answer is 4.8989However, if you're looking for the surd, you have to find two multiples of 24, one of which has to be a square number, In this case, you can have 6 and 4, as four is a square number. You can find the square root of 4, which is two, and the answer to this would then be 2 root 6.
Hope this helps :)