If this is an isosceles trapezoid, the triangles ΔSWV and ΔTWU must be congruent. Then, the corresponding sides are congruent too:
[tex]\begin{gathered} TW\cong SW \\ UW\cong VW \end{gathered}[/tex]
From the given information, we can say that:
[tex]UW=3[/tex]
Additionally, we know that:
[tex]SU=SW+UW[/tex]
Finally, using the values of SW and UW:
[tex]\begin{gathered} SU=1.7+3 \\ \\ \therefore SU=4.7 \end{gathered}[/tex]
