\(a)\sqrt{x}=11\\ \Rightarrow\sqrt{x}=\sqrt{11^2}\\ \Rightarrow\sqrt{x}=\sqrt{121}\\ \Rightarrow x=121\\ b)2\sqrt{x}=-\dfrac{13}{15}\\ \Rightarrow\sqrt{x}=-\dfrac{13}{15}:2\\ \Rightarrow\sqrt{x}=-\dfrac{13}{30}\left(ktm\right)\\ c)\sqrt{x}=\sqrt{6}\\ \Rightarrow x=6\)