I really don't understand this. Can someone help me.

Step-by-step explanation:

sum of angles of a polygon=(n-2)*180

S=(n-2)*180

n=13

S=(13-2)*180

=11*180

=1980°

2.

sum of angles=95+140+120+75+130+115+80

=750

again sum of angles of a heptagon=(7-2)×180

=5×180

=900

so these can,t be angles of heptagon.

3.

external angle of heptagon=360÷10=36

internal angle=180-36=144°

it is a convex polygon.

4.

external angle=360÷9=40°

internal angle=180-40=140°

it is a convex polygon.

5.

external angle=360÷5=72°

internal angle=180-72=108°

it is a convex polygon.

central angle of a triangle has the same measure as its intercepted arc.

step-by-step explanation:

angle efh= angle egh