Answer:
$8 per ream
Cost per ream = (Purchase value - Taxes)/Number of reams
Explanation:
Number of reams (n) = 10
Purchase value (P) = $84
Taxes (T) = $4
The cost per ream of paper is given by the total amount paid minus taxes, divided by the number of reams bought:

Each ream of paper cost $8
The equation that represents that situation is:
Cost per ream = (Purchase value - Taxes)/Number of reams