To completely factor 3x^2+12x Monica says the answer is x(3x+12). But Ashley says the answer is 3x(x+4). Who is correct, Monica or Ashley? Explain why.

I know that Ashely is right right but I'm not sure how to explain it in the right terms.

the (3x+12) term from Monica's factoring can be factored again into 3(x+4), leading to Ashely's result