The length RT is 18
The given parameters are:
This means that
RT = RS + ST
Where
RT = 3RS
So, we have
3RS = RS + ST
Evaluate
2RS = ST
Also, we have
ST = 12
This gives
2RS = 12
RS = 6
Recall that RT = 3RS
RT = 3 * 6
RT = 18
Hence, the length RT is 18
Read more about lengths at'
https://brainly.com/question/25292087
#SPJ1