Also need this answer to pls

Answer:
[tex] \large{ \tt{AC = AB + AC}}[/tex]
[tex] \longrightarrow \large \tt \: 20 = x + 3x[/tex]
[tex] \longrightarrow \large \tt \: 20 = 4x[/tex]
[tex] \longrightarrow \large \tt \: \frac{20}{4} = x[/tex]
[tex] \longrightarrow \large \boxed{\tt \: x = 5}[/tex]
Hope this helps! :)