How Does "Cross Multiplying" Even Work?

Picked one by one from a mixed channel. Transcript check: both title readers certain; 5 of 5 sampled certain picks confirmed by transcript, none failed. Channel rule: Include the calculus 'How to ... Lesson & Examples' series and descriptively titled concept, proof, or explanation videos (e.g. cross multiplying, flipping inequality signs, Law of Sines proof, the constant e). Exclude hype-titled SAT cram/tips videos, motivational talks and fun-facts items.

A 4-minute video from Math Man McGreal: “How Does "Cross Multiplying" Even Work?”.

Video by Math Man McGreal, played through YouTube's embedded player.