Since the quadrilaterals ABCD and JKLM are similar, we get that:
[tex]\frac{MJ}{DA}=\frac{JK}{AB}\text{.}[/tex]Substituting DA=5, MJ=7, AB=7, and JK=x we get:
[tex]\frac{7}{5}=\frac{x}{7}.[/tex]Multiplying the above equation by 7 we get:
[tex]\begin{gathered} \frac{7}{5}\times7=\frac{x}{7}\times7, \\ \frac{49}{5}=x\text{.} \end{gathered}[/tex]Answer:
[tex]x=9.8.[/tex]