Answer:
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Step-by-step explanation:
Given
$1000 for 9 days
$750 for 10 days
$850 for 4 days
$900 for other days
Required
Compute the daily average
First, we need to compute the number of days her balance is $900
Assuming the billing cycle is 30 days;



The Average is then calculates using:




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<em> --- Approximated</em>
A dozen people is 12. 5 people get off.
12 - 5 = 7
a=c because the transitive property states so.
The total will be $19.72 with 20% so she will get back $30.28