(√15-√12)(√15-2√3)

First, expand using the distributive property:

= √15 √15 + √15 -2√3 - √12 √15 - √12 -2√3
= 15 + (-2√45) - √180 + 2√36
= 15 - 2√45 - √180 + 12
= 27 - 2√45 - √180

Now simplify further:

27 - 2√45 - √180
= 27 - 2√(9 5) - √(36 5)
= 27 - 2(3√5) - 6√5
= 27 - 6√5 - 6√5
= 27 - 12√5

Therefore, the answer is 27 - 12√5.