You asked
Pentax k x vs pentax k 7?
Both cameras use the same Pentax K mount, the same APS-C sensor size, in-body stabilisation, and both were announced in 2009. That means they take exactly the same lenses, so the choice really comes down to the body.
The Pentax K-7 has 14.6 megapixels, against 12.4 on the Pentax K-x. The K-x runs on four AA batteries, which is handy if you'd rather not depend on a proprietary battery. For more detail, I'd pick the K-7. For a simple camera that runs on AA batteries, the K-x is the one.
For either body, I'd start with the Pentax smc DA 18-55mm f/3.5-5.6 AL WR for everyday shooting, the Pentax smc DA 50mm f/1.8 for portraits, and the Pentax HD DA 55-300mm f/4-5.8 ED WR when you need reach.
Written by Claude from this site's pages.