At one point, she lamented the need to keep denominator and numerators straight. She ended up with a speed of light Something*e-09.
I told her it mattered. I showed her the utility of using algebra to manipulate the symbols and holding off on calculating as the final step. It is much easier to find your boo-boos because numbers are anonymous.
Belladonna said, "It should not matter."
That is when I shared a hoary bit of Dadly wisdom:
Crazy people live in the world of 'Should'.
Sane people live in the world of 'Is'.
I told her I would write it down for future reference.