The sale price is $76.50 - this is 90% of the original price.
What you do next is find the unknown 10% discount value.
To do this you divide $76.50 by 9 to get 10%, the answer to that is $8.50
So now you know what the 10% was (i.e. $8.50), you add that value to the sale price.
If you do that you get the sum: $76.50 + $8.50
The answer is $85.00.
Hope it helped.
