i am in the level that i need to destroy the heavy armer its the tank but i canot i'm shooting every thing but he is steel alive how can i kill him??????????

For a tank you need a Zeuss-rocket. You can order one of your team members -with a Zeuss!- to 'attack' the tank. But I find it better to do it yourself. But then you must ofcourse choose a Zeuss-rocketlauncher at the start of the mission or at a point where you can Resupply. And in some missions you can call in an 'air strike'.. But I don't know what mission you mean.