3[(8.3-8.6)^2+(6.7-8.6)^2+(10.3-8.6)^2+(9.0-8.6)^2]
Since you do not seem to be able to use a simple calculator, I shall give you an hand :)
3*[(8.3-8.6)^2+(6.7-8.6)^2+(10.3-8.6)^2+(9.0-8.6)^2] = 20.25