To make a batch of purple frosting, you need 28 drops of blue food coloring and 21 drops of red food coloring. What is the ratio of red drops to blue drops in simplest form?

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?