Capital gain on a gifted home in Washington state

I recently sold a home that was gifted to me by my dad, who is still alive.  Purchase price was $85K in 1998.  My mom passed in 2007 and FMV for that year was $168k.  I received the home in 2012.  I'm getting confusing info on the cost basis for Washington State, which is a community property state.  

 

I've  heard I need to take 50% of my dads basis  ($85k) and 50% of my mom's stepped up basis,  (FMV of $168K), which would be $126K.  I've also been told I would just use  100% of my mom's stepped up basis of $168k to help determine the gain.  Does anyone have any insight into Washington State real estate capital gains for the situation I'm describing.  Thank you!