Suppose that 14 inches of wire costs 84 cents. at the same rate, how many inches of wire can be bought for 48 cents

I’m stuck on this i don’t understand.

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?

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=