$\begin{array}{l}
a)\,\,12.\left( {x - 2} \right) = 0\\
\,\,\,\,\,\,\,\,x - 2 = 0\\
\,\,\,\,\,\,\,\,x = 0 + 2\\
\,\,\,\,\,\,\,x = 2\\
b)\,\,{3^2} + 5x = {7^2}\\
\,\,\,\,\,\,\,9 + 5x = 49\\
\,\,\,\,\,\,\,\,5x = 49 - 9\\
\,\,\,\,\,\,\,\,5x = 40\\
\,\,\,\,\,\,\,\,x = 40:5\\
\,\,\,\,\,\,\,\,x = 8\\
c)\,\, - 45 + x = - 27\\
\,\,\,\,\,\,\,\,x = - 27 - \left( { - 45} \right)\\
\,\,\,\,\,\,\,\,x = - 27 + 45\\
\,\,\,\,\,\,\,\,x = 18\\
d)\,\,\left( {x - 47} \right) - 115 = 0\\
\,\,\,\,\,\,\,\,x - 47 = 0 + 115\\
\,\,\,\,\,\,\,\,x - 47 = 115\\
\,\,\,\,\,\,\,\,x = 115 + 47\\
\,\,\,\,\,\,\,\,x = 162
\end{array}$
Hai câu còn lại em làm tương tự nhé.
