The larger of two numbers is twice the smaller number. if 12 is subtracted from the larger number, the result is 7 more than the smaller number. find the numbers

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?