To get the 10% discount, a shopper must spend no less than $200. Use d to represent the spending (in dollars) of a shopper who gets the discount.

Answer 1

The question is a bit ill-defined. I'm going to interpret it as finding a function giving d (dollars actually spent) in terms of x (dollars spent not counting the discount). So then d would be the same as x (no discount) when x is less than 200. But when x meets or exceeds 200, the shopper gets the 10% discount, resulting in d (amount spent) being 90% of x. So when x is at least 200, we have d = 0.90 * x. We can then derive a two-case formula for d given x:

d = x (when x is less than 200)

d = 0.9x (when x is at least 200)