\(\dfrac{1}{3}\sqrt[]{9x+9}-2\sqrt[]{x+1}+8\sqrt[]{\dfrac{4x+4}{25}}=11\)
\(\Leftrightarrow\dfrac{1}{3}\sqrt[]{9\left(x+1\right)}-2\sqrt[]{x+1}+8\sqrt[]{\dfrac{4\left(x+1\right)}{25}}=11\)
\(\Leftrightarrow\sqrt[]{x+1}-2\sqrt[]{x+1}+\dfrac{16}{5}\sqrt[]{x+1}=11\)
\(\Leftrightarrow\dfrac{11}{5}\sqrt[]{x+1}=11\)
\(\Leftrightarrow\sqrt[]{x+1}=5\)
\(\Leftrightarrow x+1=25\)
\(\Leftrightarrow x=24\)