Simple Equilibrium Question... right!?

Question

In the reaction below, 6.89 atm each of Br2 and I2 were placed into a 1.00 L flask and allowed to react:
Br2(g) + I2(g) <=> 2 IBr(g)
Given that Kc = 74.0, calculate the equilibrium pressure of Br2.

The correct answer is 1.30.

How the hell are they getting that?!

I figured the equation is like this:

X^2/(6.89-X)^2 = 74

hehe, yes, i forgot to write (2x)^2, but even still, i get the wrong answer.

Answer 1

Simple mistake - its 2x squared at the beginning.