I think it’s 6.70820393 but it could be wrong
35 is best estimate hope this helps
4/7
Subtract 15 from 35 to get the remaining number of pens. 20 red pens are in the box. Divide 20 by 35 and reduce to get 4/7.
There is a difference of 11 but as a percent that would be 44%
Draw out a small graph and count the units of each side, then add all four numbers to get the perimeter.