The Definition of Porcentage is given by:
[tex]p= \frac{V_{x}}{V_{t}}[/tex]
Where Vx is discounted value or increased, and Vt is total value. The discount decreases the "p" value.
[tex]p= \frac{V_{x}}{V_{t}} \\ \frac{(100-20)}{100V_{x}} = \frac{1}{V_{t}} \\ V_{t}= \frac{51.44}{0.8} \\ \boxed {V_{x}=64.3}[/tex]
If you notice any mistake in my english, please let me know, because i am not native.
