CHALLENGE: What is the value of k?

[Brent@GMATPrepNow]

What is the value of k?

$$(1) k^2-5k-66=0$$
$$(2) \frac{2k}{k^2+5k}=\frac{1}{8}$$

Source: www.gmatprepnow.com
Answer: B
Estimated difficulty level: 600-650

[Iakgmat]

(1) yields (x+6)(x-11), which gives x=-6, 11
(2) yields k=11

So knowing (2) is sufficient.