The mean age of 5 people in a room is 28 years. A person enters the room. The mean age is now 29. What is the age of the person who entered the room?

Becca wants to mix fruit juice and soda to make a punch. she can buy fruit juice for $3 a gallon and soda for $4 a gallon. if she wants to make 28 gallons of punch at a cost of $3.25 a gallon, how many gallons of fruit juice and how many gallons of soda should she buy?