The price before tax of the books at Barnes and Noble would be 44$ - 25.1$ = 18.9$ if you use your coupon.
The price before tax of the books at Target would be 35$ - 51.1$ = -16.1$ if you use your Red card discount. However, the final price of the books cannot be negative, so the price before tax of the books at Target would be 35$ if you use your Red card discount.