3•(a-2b+3c)

Expand by distributing the 3 across the parentheses:

3 · (a - 2b + 3c) = 3a - 6b + 9c

So the simplified form is 3a - 6b + 9c. If you started from this as a factor, you can also note it's 3(a - 2b + 3c).