The maximum angle is120+5 (x-1) = 5x+115 degrees.
So the sum of internal angles = (120+5x+115) x/2 = (x-2) *180.
5x？ +235x=360x-720
5x？ - 125x+720=0
x？ -25x+ 144=0
x=9，x= 16
The convex polygon is 5x+ 1 15.
So x=9.
Data 1: Chinese deeds
While continuing to study mathematical theory, he tried to find a way to combine mathematics with industrial and agricultural