The sum of the measures of the interior angels of a convex polygon is 3240 classify the polygon by the number of sides

20-gon

Step-by-step explanation:

First we start with the formula  to find what the sum of angles will be if we know the number of sides.  

S=(n-2)*180 where S is the sum of angles and n is the number of sides.

Normally you'd plug in n to find S, but you can do the opposite too.

3240=(n-2)*180

Let me know if you need help working it from here.  

just take the area of the square and then the area of the circle then subtract the circle area from the squares area

step-by-step explanation: