Find the constant of proportionality (r) in the equation y=rx

1-for what value of x is line a parallel to line b 2-for what value of x is line a parallel to line b

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 the tip varies directly with the number of guest which equation represents between the tip, t, and the number of guest, g?