\(\left(x-1\right)\cdot x-x\cdot\left(x-3\right)=48\)
\(< ->x^2-x-x^2+3\cdot x=48\)
\(< ->2x=48\)
\(->x=24\)
,<=> (x-1-x+3)x=48
<=> 2x=48
<=> x=24
\(\left(x-1\right).x-x.\left(x-3\right)=48\)
\(\Leftrightarrow x^2-x-x^2+3.x=48\)
\(\Leftrightarrow2x=48\)
\(\Leftrightarrow x=48:2\)
\(\Leftrightarrow x=24\)