the answer is Probably C.
Since we have 2 numbers, we'll be square rooting.
All we have to do to find the mean is multiply & square root the products.
30 × 6 = 180

You can use the same process and check my answer if you'd like; I rounded the square root, so you may get a different answer.
Answer:
57 inches
Step-by-step explanation:
It rained 5*6.5+7*3.5=32.5+34.5=57 inches in the past 12 days