maths for Premiere - and other apps

learning Premiere, I have been introduced to compound effects, specifically stacking up individual stills on different video tracks, so as to display them in sequence but on a single canvas in a single frame.

while I can, painstakingly, place stills in a frame in Program Monitor using 'Scale' and 'Position', it would be great to have a resource, possibly online tutorials, giving tips and tricks to resolve layout headaches, notably the mathematical placing of object in a canvas.

The matter of mathematical tricks to resolve geometrical layouts also applies to Illustrator and, no doubt a couple of other apps.

I am not looking for solutions in After Effects, as I won't get into AE until after I have achieved solid competence in Pr.

many thanks