You asked
Pentax k 7 vs pentax k x?
The two bodies are closer than their names suggest. Both are Pentax APS-C DSLRs on the Pentax K mount, both have in-body stabilisation, and both were announced in 2009. The Pentax K-7 has the higher resolution at 14.6 megapixels, against 12.4 on the Pentax K-x, which also runs on four AA batteries. My site doesn't list the K-7's power source, so I can't say how the two compare there.
Because they share a mount, any lens below fits either body. For everyday shooting I'd start with the Pentax smc DA 18-55mm f/3.5-5.6 AL WR. For a brighter standard zoom, try the Pentax HD DA* 16-50mm f/2.8 ED PLM AW. For portraits, the Pentax smc DA 50mm f/1.8 is a cheap, sharp choice.
Written by Claude from this site's pages.