Javi distributed 3(n+2) and got 3 x n + 3 x 6. is his answer correct? prove it. someone give me a good, well-worded explanation it would a lot!

This answer is incorrect. When you distribute in algebra, you take the term(s) outside of the parentheses and multiply it or them by the inside term(s). So the correct answer here would be:
3 x n + 3 x 2     The answer above has 3 x 6 which is not correct. 
So to correctly answer the problem, you would state that the answer is not correct because in order to distribute correctly, you would multiply 3 x 2, not 3 x 6. I hope that helped!