Can somebody tell me the equation to this please ?? ASAP

Graph red beads cost $1 an ounce and gold beads cost $3 an ounce. juanita wants to purchase a 12-ounce mixture of red and gold beads that she can sell for $2 an ounce. the solution of the system shows the number of beads needed for juanita to break even. x + y = 12, x + 3y = 24 how many ounces of red beads will juanita buy to break even? how many ounces of gold beads will she buy?

You paid 28.00 for 8 gallons of gasoline. how much would you pay for 15 gallons of gasoline?

Ill mark the brainliest if you me with the these three questions 7,8,9