Episode 1 & 2 introduced SFGs as graphical representations, so now we can cover graphical manipulations in Episode 3. This will help you deepen your understanding of how SFGs and equation systems are related.
Beware: Around 4:30, the bottom-right node should be w, not z. Also, Around 8:30, two equations are shown, they are correct, but when I read them out loud, I switch the names of the variables. Finally, around 9:00, the sign is wrong. The last equation should be x=-y*(d/a). Typical mistakes of mine :)