Since the pond is located exactly halfway between Louis and the mountain, then to find its coordinates, you can use the formula to determine the midpoint of a segment
[tex](\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})[/tex]In this case, you have
[tex]\begin{gathered} (x_1,y_1)=(500,1259) \\ (x_2,y_2)=\mleft(250,129\mright) \end{gathered}[/tex][tex](\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})=(\frac{500+250}{2},\frac{1259+129}{2})=(\frac{750}{2},\frac{1388}{2})=(375,694)[/tex][tex](\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})=(375,694)[/tex]Therefore, the coordinates Louis should use to represent the location of the pond are (375,694).