Tìm x, biếta) \(15+3x=3\)b) \(1\frac{3}{2}x - \frac{6}{7} = \frac{1}{8}\)

a) \(15 + 3x = 3\)

\(\begin{array}{l}
3x = 3 - 15\\
3x =  - 12\\
x =  - 12:3\\
x =  - 4
\end{array}\)

b) 

\(\begin{array}{l}
1\frac{3}{2}.x - \frac{6}{7} = \frac{1}{8}\\
\frac{5}{2}.x = \frac{1}{8} + \frac{6}{7}\\
\frac{5}{2}.x = \frac{{7 + 48}}{{56}} = \frac{{55}}{{56}}\\
{\rm{    }}x = \frac{{55}}{{56}}:\frac{5}{2}\\
{\rm{    }}x = \frac{{55}}{{56}}.\frac{2}{5}{\rm{  = }}\frac{{11}}{{28}}
\end{array}\)