In math class, students must randomly draw a card that contains an equation that they must graph on the board.

If the cards contain the following equations, what is the probability that a student will graph a line whose slope is 3?

3y = 9x + 3
x(x + 3) = 0
3x + y = 0
x = 3y
x 2 + 3 = 0
y - 3x = 0

Answer choices: (1/6, 1/3, 1/2, 2/3)