Answer:
(Choice A) 5M
Step-by-step explanation:
Let total no. of e-mails in inbox be x
Since she read 80 % of mails i.e 80 % of x
⇒[tex]80\% \times x[/tex]
⇒[tex]\frac{80}{100}\times x[/tex]
⇒[tex]0.8 x[/tex]
So, she read 0.8x e-mails.
So, remaining email = total e-mails - read e-mails
[tex]=x-0.8x[/tex]
Since we are given that Danette still has M unread e-mails.
⇒ [tex]M=x-0.8x[/tex]
⇒ [tex]M=x(1-0.8)[/tex]
⇒ [tex]M=x\times 0.2[/tex]
⇒ [tex]\frac{M}{0.2}=x[/tex]
⇒ [tex]\frac{10M}{2}=x[/tex]
⇒ [tex]5M=x[/tex]
Thus the expression represent the number of e-mails Danette had in her inbox before she started reading is 5M.
Hence Choice A is correct.
