1. **State the problem:** Melanie uses 5 screws per plank and buys 100 screws. We need to find how much wood she buys, then compare costs at Home Depot and Rona with discounts, and finally calculate the final price after an extra 10% discount and 13% tax. 2. **Find how many planks Melanie buys:** Since 5 screws are used per plank, the number of planks is $$\frac{100}{5} = 20$$ planks. 3. **Calculate total wood length:** Each plank is 8 feet, so total wood length is $$20 \times 8 = 160$$ feet. 4. **Calculate costs at Home Depot:** - Wood price per foot: 6 (regular price) with 20% off means price is $$6 \times (1 - 0.20) = 6 \times 0.80 = 4.8$$ per foot. - Screws price each: 0.10 with 25% off means price is $$0.10 \times (1 - 0.25) = 0.10 \times 0.75 = 0.075$$ each. - Total wood cost: $$160 \times 4.8 = 768$$ - Total screws cost: $$100 \times 0.075 = 7.5$$ - Total cost at Home Depot: $$768 + 7.5 = 775.5$$ 5. **Calculate costs at Rona:** - Wood price per foot: 6.50 with 25% off means price is $$6.50 \times (1 - 0.25) = 6.50 \times 0.75 = 4.875$$ per foot. - Screws price each: 0.06 with 50% off means price is $$0.06 \times (1 - 0.50) = 0.06 \times 0.50 = 0.03$$ each. - Total wood cost: $$160 \times 4.875 = 780$$ - Total screws cost: $$100 \times 0.03 = 3$$ - Total cost at Rona: $$780 + 3 = 783$$ 6. **Compare costs:** Home Depot total: 775.5 Rona total: 783 Melanie should buy from Home Depot because it is cheaper. 7. **Apply additional 10% discount at Home Depot:** Discounted price: $$775.5 \times (1 - 0.10) = 775.5 \times 0.90 = 697.95$$ 8. **Apply 13% tax:** Final price: $$697.95 \times (1 + 0.13) = 697.95 \times 1.13 = 788.6835$$ **Final answer:** Melanie pays approximately 788.68 after all discounts and taxes.