Answer
$$A \approx 228.25{\text{y}}{{\text{d}}^2}$$
Work Step by Step
$$\eqalign{
& a = 25.4{\text{yd}},\,\,\,b = 38.2{\text{yd,}}\,\,\,c = 19.8{\text{yd}} \cr
& {\text{First}},{\text{ find the semiperimeter }}s \cr
& s = \frac{1}{2}\left( {a + b + c} \right) \cr
& s = \frac{1}{2}\left( {25.4 + 38.2 + 19.8} \right) \cr
& s = 41.7 \cr
& \cr
& {\text{Now use Heron's formula to find the area }}A \cr
& A = \sqrt {s\left( {s - a} \right)\left( {s - b} \right)\left( {s - c} \right)} \cr
& A = \sqrt {41.7\left( {41.7 - 25.4} \right)\left( {41.7 - 38.2} \right)\left( {41.7 - 19.8} \right)} \cr
& {\text{Use a calculator}} \cr
& A \approx 228.25{\text{y}}{{\text{d}}^2} \cr} $$
