What equation? There’s none there
For the general case, the n-gon, you got

degrees. The 13-gon thus has 1980 degrees in total.
Answer:
y = 1/2
Step-by-step explanation:
x = -5y+2
x=3y-2
substitute for x ans solve
3y-2=-5y+2
8y-2=2
8y = 4
y= 4/8
y=1/2
they fill a plane --- finite or infinite without gaps or overlaps
AND
no spaces or overlaps exist between its pieces
sorry if im wrong