Explain a "rain check"

a ticket given for later use when a sports event or other outdoor event is interrupted or postponed by rain.

a coupon issued to a customer by a store, guaranteeing that a sale item that is out of stock may be purchased by that customer at a later date at the same reduced price.

Explanation:

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

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i think the answer would d