The third one because it matches plus im copy
3.9x+0.8y is the answer to your question.
Octagon - 135 degrees
Decagon - 144 degrees
135 / 144 * 100% = 93.75%
Therefore it is 6.25% less
source 1728.com/polygon.htm
1.033x10^3 4.2x10^4
I hope they are right !! :)
