[tex]\\ \sf\dashrightarrow \dfrac{x+20}{2}=3x[/tex]
[tex]\\ \sf\dashrightarrow x+20=2(3x)[/tex]
[tex]\\ \sf\dashrightarrow x+20=6x[/tex]
[tex]\\ \sf\dashrightarrow 20=6x-x[/tex]
[tex]\\ \sf\dashrightarrow 5x=20[/tex]
[tex]\\ \sf\dashrightarrow x=\dfrac{20}{5}[/tex]
[tex]\\ \sf\dashrightarrow x=4[/tex]
