Answer: It's not equal to 20% discount.
Step-by-step explanation:
Let's assume the cost of a good is $100. Since there's 10% off on every item, the cost of the good will be:
= $100 - (10% × $100)
= $100 - $10
= $90
Since the coupon states that one will receive an additional 10% off, therefore the amount that the person will pay will be:
= $90 - (10% × $90)
= $90 - (0.1 × $90)
= $90 - $9
= $81
If the same good is $100 and there's a 20% discount, the amount that'll be paid will be:
= $100 - (20% × $100)
= $100 - (0.2 × $100)
= $100 - $20
= $80
Therefore, it's not equal to 20% discount.