Answer
$-2a+4$
Work Step by Step
We start with the given expression: $2(a-1)-a-3(a-2)$
We use the distributive property to expand the expression: $2a-2-a-3a+6$
We use the commutative property to group like terms: $2a-a-3a+6-2$
We combine the like terms using subtraction: $-2a+4$