Answer
$$2ca+cb+3c^2. $$
Work Step by Step
By multiplying each term by c, and then adding the products, we have
$$c(2a+b+3c)= c(2a)+c(b)+c(3c)\\
=2ca+cb+3c^2. $$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.