√150 - 3√6 = 2√6
Find the factors of 150 which has a square root.
√25 * √6 - 3√6 *25 and 6 are the factors of 150, 25 has a square root of 5.
5√6 - 3√6 * since both numbers have the same value of radicals, you can now perform subtraction, only subtract the whole numbers and carry over the radical.
5√6 - 3√6 = 2√6