\[\left( \sqrt{20} \right)^{2} - \ \sqrt[5]{39^{2}} + \left( \sqrt[6]{18^{3}} \right)^{2} =\]
\[= 20 - 39 + \sqrt[6]{\left( 18^{3} \right)^{2}} =\]
\[= - 19 + \sqrt[6]{18^{6}} =\]
\[= - 19 + 18 = - 1\]