a)
\(5x-30=0\\ \Leftrightarrow5x=30\\ \Rightarrow x=\frac{30}{5}=6\)
b)
\(7-4x=3\cdot\left(x+1\right)-2x-2\\ \Leftrightarrow7-4x=3\cdot\left(x+1\right)-2\cdot\left(x+1\right)\\ \Leftrightarrow7-4x=\left(3-2\right)\cdot\left(x+1\right)\\ \Leftrightarrow7-4x=x+1\\ \Leftrightarrow7-4x-x-1=0\\ \Leftrightarrow6-5x=0\\ \Rightarrow x=\frac{6}{5}\)