\(\left(3-\dfrac{1}{2}\right)x=13\\ \left(\dfrac{6-1}{2}\right)x=13\\ \dfrac{5}{2}x=13\\ x=13:\dfrac{5}{2}\\ x=\dfrac{26}{5}\)
3 x-\(\dfrac{1}{2}\) x=13 \(\leftrightarrow\) \(\dfrac{5}{2}\)x=13 \(\leftrightarrow\) x=13: \(\dfrac{5}{2}\)\(\leftrightarrow\) x=\(\dfrac{26}{5}\)