In a parallelogram opposite sides have the same length therefore, for figure EFGH to be a parallelogram we must have that:
[tex]GF=HE[/tex]
Substituting we get:
[tex]z+10=2z[/tex]
Now, we solve for "z". First, we subtract "z" from both sides:
[tex]\begin{gathered} z-z+10=2z-z \\ 10=z \end{gathered}[/tex]
Therefore, the value of "z" is 10.
