Oscar is buying some headphones for $18 will have to pay 8% in sales tax. how much will Oscar pay in taxes?

Iwant to know what 3g+5h+4g-2h is my teacher is too selfish to tell us

Money off coupons have been circulated to 300 households. only 2/5 of these were redeemed (used) in the local supermarket to get a free shampoo. what fraction of coupons were unused? (ps: write how you got the answer)

Yo need asap pls ! markin da brainiest too !