If you cards are only 5,6,7, then the probability of getting even, then even would be zero.
The directions say that the card is not replaced. Therefore, once you pick the 6, there would be no more even cards.
If you would like to write the equation in the above form, you can calculate this using the following steps:
x^2 - 8x + 13 = 0
(x - 4)^2 = x^2 - 8x + 16
(x - 4)^2 - 3 = 0
(x - 4<span>)^2 = 3
</span>
The correct result would be (x - 4<span>)^2 = 3.</span>
