Answer
Find out the number of student the entire class.
To prove
Formula
[tex]Percentage = \frac{Part\ value\times100}{Total\ value}[/tex]
As given
According to the scores on the last math test, 80%, or 20, of the students in the class received an A.
i.e
Percentage = 80 %
Part value = 20
put in the formula
[tex]80 = \frac{20\times100}{Total\ value}[/tex]
[tex]Total\ value = \frac{20\times100}{80}[/tex]
[tex]Total\ value = \frac{2000}{80}[/tex]
Total value = 25
Therefore the total number of student in the entire class be 25.