It would be 600 + 50 + 8 + 0.1 + 0.02 + 0.009
We are asked to find the area of patio. It is circular so formula used for area is given by:

Where
r = radius = diameter / 2 = 20 / 2 = 10 feet

When we round this to the nearest whole number:
The answer to your question
is 12
4, 16
-1, 1
3, 9
12, 144
16, 256
The rule is y=x^2. If you square all the numbers on the x side, you will get the numbers on the y side. 4 times 4 = 16. -1 times -1 =1. 3 times 3 =9, and so on.