\(a\text{) }\frac{x+1}{3}=\frac{-7}{3}\)
\(\Leftrightarrow x+1=-7\)
\(\Leftrightarrow x=-8\)
Vậy: x = -8.
\(b\text{) }\frac{3}{11-x}=\frac{7}{8}-\left(-\frac{1}{8}\right)\)
\(\Leftrightarrow\frac{3}{11-x}=1\)
\(\Leftrightarrow11-x=3\)
\(\Leftrightarrow x=8\)
Vậy; x = 8.