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Out of these 9 coupons, in 7 chances, we can select coupons in 9 7 ways. But this will also include cases when 9 is not selected at all, and thus, the highest number that is selected is 8. This can be done in 8 7 ways (i.e. 8 coupons in 7 chances). Thus, favourable cases for 9 to be largest in the selected coupon, number of cases = 9 7 − 8 7
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