How do you do #9? ? i know what the answer is but idk how to get to it

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?

Suppose i flip two identical coins. what is the probability that i get one head and one tail?

Solve the system of equations y= 3/2 - 1, -x+ y =-3