Answer
$$A \approx 308.63{\text{i}}{{\text{n}}^2}$$
Work Step by Step
$$\eqalign{
& a = 22{\text{in}},\,\,\,b = 45{\text{in,}}\,\,\,c = 31{\text{in}} \cr
& {\text{First}},{\text{ find the semiperimeter }}s \cr
& s = \frac{1}{2}\left( {a + b + c} \right) \cr
& s = \frac{1}{2}\left( {22 + 45 + 31} \right) \cr
& s = 49 \cr
& \cr
& {\text{Now use Heron's formula to find the area }}A \cr
& A = \sqrt {s\left( {s - a} \right)\left( {s - b} \right)\left( {s - c} \right)} \cr
& A = \sqrt {49\left( {49 - 22} \right)\left( {49 - 45} \right)\left( {49 - 31} \right)} \cr
& {\text{Use a calculator}} \cr
& A \approx 308.63{\text{i}}{{\text{n}}^2} \cr} $$
