Answer:
Option D RX=4 units
Explanation:
we know that
In the right triangle RTS
The cosine of angle TRS is equal to
cos(TRS)=RT/RS
substitute
cos(TRS)=6/9 -----> equation A
In the right triangle RTX
The cosine of angle TRX is equal to
cos(TRX)=RX/RT
substitute
cos(TRX)=RX/6 -----> equation B
∠TRS=∠TRX -----> is the same angle
Match equation A and equation B
6/9=RX/6
RX=6*6/9=4 units