Question

After reading 80% of her emails in her inbox, Danette still has M unread emails.

Answer 1

answer : option A and B

After reading 80% of her emails in her inbox, Danette still has M unread emails

M unread emails

Let x be the number of emails before reading

80% of emails are left in the box. So, 0.08x emails are left in the box

Now we make an equation

number of emails - 80% of unread emails= number of unread mails

x - 0.08x = M

Now we factor out x

x ( 1- 0.08) = M

So
`x = (M)/(1-0.8)`

or
`x = (M)/(0.2)= 5M`

Answer 2

`(M)/(1-0.8)` and
`5M`

Explanation:

1. Let's imagine that you have 100 e-mails unread. When you read 80% of these e-mails you have the following amount
`M` unread:

`100-(0.8)(100)=20` e-mails

2. If you substitute 20 e-mails into the equations shown above, you will obtain the original amount:

`(20)/(1-0.8)=100\\5(20)=100`