As per the problem we can see that
There two triangles with equal corresponding sides.
So we can set up the equation as below:
[tex] 7x-4=31\\
\\
\text{Add 4 on both the sides we get}\\
\\
7x-4+4=31+4\\
\\
7x=35\\
\\
\text{Divide both the sides by 7 we get}\\
\\
x=5\\ [/tex]
Hence the value of x is 5.
