AC = 2AD (T30°) => AC = 12√3 cm
CD = √AC² - AD² = √144·3 - 36·3 = √3(144-36) = √3·108 = √324 = 18 cm
AD² = CD·DB
108 = 18·DB => DB = 108/18 = 6 cm
BC = CD + DB = 18 + 6 = 24 cm
A(ΔABC) = AD·BC/2 = 24·6√3/2 = 72√3 cm²
ED = CD/2 (T30°) = 18/2 = 9 cm
CE = √CD² - ED² = √324 - 81 = √243 = 9√3 cm
A(ΔCDE) = 9·9√3/2 = 81√3/2 cm²
A(ΔCDE)/A(ΔABC) = (81√3/2)/(72√3) = 81/144 = 9/16
