Find greater x value of a curve that corresponds to a y value

[DomFirth]

I want to find the x value which corresponds which half the maximum of the y value, and i want the x value to be greater than the x value which corresponds to the maximum y value

So if you had a curve, and you looked at where the y corresponds to the x there would be 2 values. I want to find only the larger value x value, but cannot seem to do this using lookups