\(b,\left(2x+1\right).\left(39-2\right)=-55\)
\(\Rightarrow\left(2x+1\right).37=-55\)
\(\Rightarrow3x+1=-\frac{55}{37}\)
\(\Rightarrow3x=-\frac{92}{37}\)
\(\Rightarrow x=-\frac{92}{111}\)
\(c,\left(x-7\right)\left(x+3\right)< 0\)
\(\Rightarrow\orbr{\begin{cases}x-7>0;x+3< 0\\x-7< 0;x+3>0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x>7;x< -3\\x< 7;x>-3\end{cases}}\)