A bathtub is draining at a constant rate. After 2 minutes, it holds 30 gallons of water. Three minutes later, it holds 12 gallons of water. Write an equation the represents the number of y of gallons of water in the tub after x minutes.

Let x, represent the number of minutes and y represents the number of gallons of water in the tub, then the ordered pairs (2, 30) and (5, 12) satisfies the equation.

Therefore the equation is given by: (y - 30) / (x - 2) = (12 - 30) / (5 - 2)

(y - 30) / (x - 2) = - 18/3 x = - 6

y - 30 = - 6 (x - 2) = - 6x + 12

y = - 6x + 42

Required equation is y + 6x = 42.