Excel work need help

Plz finish those step by step, don’t just give answers without formula calculation.

This work contains 5 chapters, and I’ll provide sample form and solutions. Btw, the soulutions of the questions are almost same with my questions, just changed number.

"Our Prices Start at $11.99. As Our First Client, Use Coupon Code GET15 to claim 15% Discount This Month!!":

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