Answer:
12(1 - y) and 12(1- z).
Step-by-step explanation:
Cost of a base ball = $20
Cost of the base ball after a discount coupon of x% = $20 - x% of $20
= $20(1 - x)
Similarly cost of a tennis ball with y% discount = $12(1 - y)
And cost of soccer ball = $15
So the total cost of Monique's purchase = 20(1 - x) + 15 + 12( 1 - y)
Here 12(1 - y) represents the price of the set of tennis balls after coupon z was applied.
If other coupon of z% is applied on total purchase of Monique, then the cost will be = (10 + 15 + 12) - z% of (10 + 15 + 12)
= (10 + 15 + 12)(1 - z)
In this expression 12(1 - z) represents the cost of a pair of tennis balls after z% discount on total purchase.