From the information we have, the original price is 825 $. We now need to calculate 1/4 of that price, so:
1/4 * 825
825/4 = 206.25
Mark also wanted to use the 1/5 coupon off the sale price, so we calculate this:
1/5 * 825
825/5 = 165
Now we add both discounts :
206.25 + 165 = 371.25
Now we subtract this from original sale price:
825 - 371.25 = 453.75
He bought the tablet at 453 dollars and 75 cents.