A = pi × r^2 = pi × (d/2)^2
So A(large) - A(small) =
[tex]\pi {(12 \div 2)}^{2} - \pi {(8 \div 2)}^{2} \\ = \pi {(6)}^{2} - \pi {(4)}^{2} = 36\pi - 16\pi \\ = 20\pi \: {in}^{2} = 20 \times 3.1415 \: {in}^{2} \\ = 62.8 \: {in}^{2} = 63 \: {in}^{2} [/tex]
