Respuesta :
Answer: The required length of QS is 42 units.
Step-by-step explanation: Given that R is the midpoint of QS, where
[tex]QS=8x-51,~~RS=3x-6.[/tex]
We are to find the length of QS.
Since R is the midpoint of the segment QS, so we must have
[tex]QR=RS\\\\\Rightarrow 8x-51=3x-6\\\\\Rightarrow 8x-3x=51-6\\\\\Rightarrow 5x=45\\\\\Rightarrow x=\dfrac{45}{5}\\\\\Rightarrow x=9.[/tex]
Therefore, the length of QS is given by
[tex]QS\\\\=QR+RS\\\\=8x-51+3x-6\\\\=11x-57\\\\=11\times9-57\\\\=99-57\\\\=42.[/tex]
Thus, the required length of QS is 42 units.