Compare simplifying before multiplying fractions with simplifying after multiplying the fractions

We will start using a new way to indicate simplifying fractions. When a numerator or

a denominator gets simplified, we will cross it out with a slash and write the new

numerator or denominator next to it (either above it or below it). The number you divide by (the 4) does not get indicated in any way! You only

think about it in your mind: "I divide 12 by 4, and get 3. I divide 20 by 4, and get 5." You may not see any advantage over the "old" method yet, but this shortcut will

come in handy soon.