Answer: The correct options are.....
A) [tex]\frac{M}{1-0.8}[/tex] and
B) [tex]5M[/tex]
Step-by-step explanation:
Suppose, the number of e-mails Danette had in her inbox before she started reading was [tex]X[/tex].
Percentage of read emails is 80%, so the number of read emails [tex]= (\frac{80}{100}*X)=0.8X[/tex]
Thus, the number of unread emails [tex]= X-0.8X=X(1-0.8)[/tex], which is given as [tex]M[/tex].
So, the equation will be........
[tex]X(1-0.8)=M\\ \\ \Rightarrow X=\frac{M}{1-0.8} (Answer: 1) \\ \\ \Rightarrow X=\frac{M}{0.2}\\ \\ \Rightarrow X=(\frac{1}{0.2})M=5M (Answer: 2)[/tex]
Thus, the expressions which could represent the number of e-mails Danette had in her inbox before she started reading are: [tex]\frac{M}{1-0.8}[/tex] or [tex]5M[/tex]