Who can help me answer these questions 6-9?

In the reaction between a crushed antacid tablet and vinegar what gas is emitted

4. glenn andrews recently bought a motorcycle for $3,950. if he had to pay 6% sales tax on the bike, what was the total cost of the motorcycle?

How is it possible for someone to put an ear to a wall and hear someone in the next room?     a. sound waves can travel though solids.    b. the waves travel from room to room via air.    c. there must be some air in the wall so the sound can travel through it.    d. sound waves change to electromagnetic waves and then back again.