But the answer to the 20ml + 30ml question could lead to conservation of energy and matter issues, so assuming two liquids that aren't going to react or change state, will end up being 50ml.

When I went back to college after ten years away, one of the professors complimented me and said, "it's nice to see someone write a paper that knows what a complete sentence is."

That was 1981. Has it gotten worse?