Midpoints
B is the midpoint of AC , find x.

B is the midpoint which means both sides are equal to each other:
5x = 3x + 4
Subtract 3x from both sides
2x = 4
Divide both sides by 2
X = 2
[tex]\red{➤}\:[/tex][tex]\sf AB = 5x [/tex]
[tex]\red{➤}\:[/tex][tex]\sf BC = 3x+4[/tex]
[tex]\\[/tex]
[tex]\orange{☛}\:[/tex][tex]\sf Value \:of \:x[/tex]
[tex]\\[/tex]
Since B is midpoint of AC, therefore -
[tex]\\\quad\quad\quad\quad\sf AB = BC [/tex]
[tex]\begin{gathered}\\\quad\longrightarrow\quad \sf 5x = 3x+4\quad\quad ( Putting \:Value) \\\end{gathered} [/tex]
[tex]\begin{gathered}\\\quad\longrightarrow\quad\sf 5x-3x =4 \\\end{gathered} [/tex]
[tex]\begin{gathered}\\\quad\longrightarrow\quad\sf 2x =4 \\\end{gathered} [/tex]
[tex]\begin{gathered}\\\quad\longrightarrow\quad\sf x =\frac{4}{2}\\\end{gathered} [/tex]
[tex]\begin{gathered}\\\quad\longrightarrow\quad\boxed{\sf {x=2 }}\\\end{gathered} [/tex]