Answer :
The cost price of the watch is $y.
The expression for the loss is,
[tex]\begin{gathered} loss=y\times\frac{15}{100} \\ =0.15y \end{gathered}[/tex]The selling price can be determined as,
[tex]\begin{gathered} SP=CP-\text{loss} \\ =y-0.15y \\ =0.85y \end{gathered}[/tex]Thus, 0.85y is the correct answer.