If you can't
the quad's radius is 6 in and the circumference is 12 in
the penta's radius is 6.5 in and the circumference is 9.5 in
the hex's radius is 7.2 in and the circumference is 6.2 in
the octo's radius is 6.6 in and the circumference 5.5 in

The circumference of a circle has the formula: 2*pi*r. So, we could easily determine the value of r.

C = 2*pi*r
12*pi = 2*pi*r
12 = 2r
r = 12/2
r = 6 inches

Knowing the r, we could find the area which has the formula

A = pi*r^2
A = pi*6^2
A = 113.1 square inches

Hope this helps!