How do i make the different values of two properties change at the same amount in After Effects? I want to make the value of the Point of Interest of a camera change at the same amount i change the Position, but when i simply pick whip parent the Point of Interest to the position, the former takes the same value as the later, which is not the result i expected. How do i accomplish the expected result?
Pick-whipping one value to another sets it to that value, if you don't want them to be the same but rather change at the same rate then try this instead: 

value + transform.position


Alternatively, parenting the whole camera to a 3D null object may make things easier to animate and is generally nicer to deal with. 

The Angle Script will create a new camera parented to a null for you, which makes things a lot easier: https://madebyloop.co.uk/products/angle-streamline-camera-null-control-after-effects/