Simplifying square roots is done by finding perfect square factors (other than 1) of the radicand (the expression inside a radical). If there are no perfect square factors of the radicand, the square root cannot be simplified.
So we will be looking for perfect square factors of your radicand, 24. Among the factors of 24, only one is a perfect suqare: 4. So we rewrite the square root in a factored form, using the perfect square factor:
Next we use a property of radicals, to separate the factors into their own square roots:
Now that the perfect square factor is in its own square root, we can replace it. Since we will replace it with 2: