"3/4 of a cake in 5 minutes" is a verbal equation. We can divide both sides (that is, 3/4, 5 min) by 5 to determine the number of cakes I can bake in 1 minute:
This is the fundamental zero additive rule x - 0 = x which means that for the set of real numbers, there exist a number such that if added (or subtracted) from any other will not affect such number.