\(12^2x=56-\left[\left(-10\right).13x\right]\)
\(\Leftrightarrow144x=56-\left(-130x\right)\)
\(\Leftrightarrow144x=56+130x\)
\(\Leftrightarrow144x-130x=56\)
\(\Leftrightarrow14x=56\)
\(\Leftrightarrow x=4\)
...
\(\left(12\right)^2.x=56-\left[\left(-10\right).13.x\right]\)
\(=>144x=56-\left(-130x\right)\)
\(=>144x=56+130x\)
\(=>144x-130x=56\)
\(=>14x=56\)
\(=>x=\frac{56}{14}=4\)