My tahoe wont start,turns over fine,it acts like its not getting gas but tank is half full?

Could be the fuel pump, it's a pretty common failure. The electric pump is in the tank. When you turn the key to the run position you should be able to hear a faint hum or buzzing from the tank. If it does not sound like its running (need to have it absolutely quiet to hear pump) check for a blown fuse. Sometimes they will have one last gasp in them and you can get them to work by banging on the bottom of the tank while someone else turns the key. I have had this work several times but not always. It will do two things for you, saves a tow bill, and confirms the pump is bad. If that does get it going drive it straight to you mechanic, you wont get a second chance.