11 units
Step-by-step explanation:
Step 1:
From the figure indicated Total Length SU = 20 units
Length of ST = 9 units
Length of TU = To be found
Step 2:
From Figure [tex]ST+TU=SU\\[/tex]
[tex]TU=SU-ST[/tex]
[tex]TU=20-9[/tex]
[tex]TU=11[/tex] units
