Gosh, this isembarrassing! >_<so

I have done these dozens of times! But I'm having a bad day, and can't seem to wrap my brain around it.

It's the whole squared x that is frustrating me.

So...

Solve for x;

x^2 - 15x + 36 = 0

Gah! I really don't know why my brain isn't comprehending this.