\(a,7x-\left(3-5x\right)=4x+11.\\ \Leftrightarrow7x-3+5x-4x-11=0.\\ \Leftrightarrow8x=14.\\ \Leftrightarrow x=\dfrac{7}{4}.\)
\(b,\dfrac{x+1}{2}-\dfrac{x}{3}=\dfrac{1}{2}.\\ \Rightarrow3\left(x+1\right)-2x=3.\\ \Leftrightarrow3x+3-2x=3.\\ \Leftrightarrow x=0.\)
\(c,x^2-25=\left(2x+5\right)\left(5-x\right).\\ \Leftrightarrow\left(x-5\right)\left(x+5\right)+\left(2x+5\right)\left(x-5\right)=0.\\ \Leftrightarrow\left(x-5\right)\left(x+5+2x+5\right)=0.\\ \Leftrightarrow\left(x-5\right)\left(3x+10\right)=0.\\ \Leftrightarrow\left[{}\begin{matrix}x-5=0.\\3x+10=0.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5.\\x=-\dfrac{10}{3}.\end{matrix}\right.\)
