[tex]a)A= \frac{a^2 \sqrt{3} }{4}= \frac{(8 \sqrt{3})^2 \sqrt{3} }{4}=48 \sqrt{3} cm^2 \\ b)12^2=x^2+x^2;144=2 x^{2} ; x^{2} =72;x=6 \sqrt{2};A= x^{2} =72cm^2 \\ c)A= \frac{1}{2} AB*AC*sinA= \frac{1}{2}*6,4*15*sin150= 48* \frac{ \sqrt{3} }{2}=24 \sqrt{3}cm^2 [/tex]