Answer: 60√2
Explanation: We can combine the 6 and 12 because they are both under the radical and get 10√72.
We can simplify the √72 to √(36*2), which becomes 6√2.
We can then multiply the 6 and 10 (both are outside the radical) to get 60√2.
If you check both my answer and the problem in the question, you get approximately 84.9.