A math sentence involving multiple operations is evaluated according to the Order of Operations. Multiplication is done left to right.
(8) × (-6) × (-3)
= ((8) × (-6)) × (-3)
= (-48) × (-3)
= 144
_____
The associative and commutative properties of multiplication allow you to rearrange this to any convenient order. You can also remove factors of -1 from the negative numbers and deal with those separately, if you like.
8 × -6 × -3
= 8 × -1 × 6 × -1 × 3
= (-1)×(-1) × 8 × 6 × 3
= 1 × 8 × 6 × 3
= 8 × 6 × 3 . . . . . . 1 times anything is that thing. That's the multiplicative identity property.
= 3 × 6 × 8 . . . . . if you want. (Order for multiplication of numbers doesn't matter. It does matter when multiplying certain other things, like matrices or vectors.)