Can we add marker in google Map using XY co ordinates

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ASP.NET

Google-Maps

Hi I am using Google map in my application.
I am adding marker on Google map by using LAT/LONG of the point as shown below

var marker = new google.maps.Marker({ position: new google.maps.LatLng(LatValue,LongValue), map: map, title: MyTitle, icon:MyIcon });

But it is found that in my case instead of LAT/LONG values , XY co ordinates are available.
So can we plot marker using XY co ordinates something like this

var marker = new google.maps.Marker({ position: new google.maps.LatLng(X Co ordinate,Y Co ordinate), map: map, title: MyTitle, icon:MyIcon });

Is there any formula/method of converting XY co ordinate to LAT/LONG?
Thanks & Regards,
Anirudha Deshpande