3√6(√6-2√10)

To simplify this expression, we first need to distribute 3√6 to (√6) and (-2√10).

3√6(√6) = 3√6 * √6 = 3√(6 * 6) = 3√36 = 3 * 6 = 18

3√6(-2√10) = 3√6 * -2√10 = -6√(6 * 10) = -6√60 = -6√(2 * 30) = -6√(2 * 2 * 15) = -12√15

So, the simplified expression is 18 - 12√15.