What do you mean by "best fits these results". You are given 7 data points so there exist a sixth degree polynomial that exactly passes through those 7 points.
You could set this up as and then let x and y be from each data point to get 7 equations to solve for the 7 coefficients. For example, when x= 0, y= 20 so .
On the other hand there are probably simpler functions (linear, quadratic, etc.) that come close to those points.