Answer:
please see analysis
Step-by-step explanation:
[tex]\left\{\right.{ \triangle}\ RST\cong { \triangle}\ DE[/tex]F
[tex](SSS\ Congruence\ Postulate)[/tex]
[tex]2.\ { \triangle\ CAT\cong { \triangle\ BED\ \left\{\right.Given\left.\ \right\}[/tex]
[tex]\bar{AT}\cong\bar{ED}[/tex]
[tex]\overline{AT}=20[/tex]
[tex]so\ \overline{ED}=20[/tex]
[tex]DE=3x-7=20\rightarrow\ x=9[/tex]
I hope this helps you:)
