Question

Use function notation to describe the point(2,12.50)

Answer 1

There are an infinite number of different functions that could have 
(2, 12.5) as one of their points.

-- If the function is linear (a straight line), then we need two points to
determine what the function is.

-- If the function is not linear (a curved graph), then we need more than that.

With only one point, we can't even tell whether or not the function is linear.