How is the needed equity calculated here?
If you want to know breakeven equity you need,you have to convert pot odds to fraction and then to percentage.
You have pot odds 2:1 :
1) convert to fraction 1/2+1= 1/3 (2+1 is a whole)
2)covert fraction to percentage 1/3=0.33 or 33% 33% breakeven equity you need.
You can find odds to percentage charts in most books or do it yourself and remember most popular:
Odds Fraction Percentage
1:1 1/2 50%
2:1 1/3 33%
3:1 1/4 25%
4:1 1/5 20%
imho calculations in your notes seems not right.