I can't read that language but I'll guess it says write a second degree equation then solve for n when d=10.



Answer: n² - 3n - 20 = 0
That doesn't factor so there is no integer n solution.
That means there are no polygons with 10 diagonals.

The answer is 3.92%
Explanation
Do 2 divided by 51
0.03921
Multiply your answer by 100
3.9215
Round to the nearest tenth
3.92%
The answer to your problem is 3^1..