6ab + a(a – b – 6b) + 4a(2b +a) – ab , para a= -1 e b=2

ME AJUDEM! É URGENTE

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?