Which of the following is a quadratic equation?
x(x - 4) = 2x + x 2 - 7
5(2y + 3) - 6y = 5y(y 2 - 8y)
k(k + 1) - k(k - 2) 2k = 0
p(p 2 + 7) = p 2 + p 3 - 18
In a class of 17 students, each scored differently. A's rank from the top is 9th, while B's rank from the bottom is 11th. C's rank from the top is better than A but worse than B. What is C's rank from the top?