3d interpolation of a table

Not sure sure if this the right forum but I am struggling with this problem.

I want to obtain a number from a table which may need to be interpolated on both axis.
y
x 3 4 5
3 109.8 108.7 108.1
4 108.7 107.4 106.6
5 108.3 106.8 105.9
6 107.9 106.2 105.3
7 106.8 105.9 104.8
8 107.2 105.5 1074.4
9 107 105.3 104.2

So trying to find the intersecting result that would be 5.5 on x and 3.5 on y.

Not sure if it is actually possible, any sort of help would be much appreciated.

Are you looking for something sophisticated like a linear regression type interpolation or would this be something like, 3.5 is halfway between 3 and 4, 5.5 is between 5 and 6, take the average of coordinates (3,5), (3,6), (4,5), (4,6)?

Check this file.

Thanks guys, this is exactly what I was looking for.

Thanks again