How do I change the belts, there's no tensioner!?

I can't figure this out, one belts goes from the crank to the compressor, and the other from the crank to the water pump and alternator. Theres no other pullys or tensioner. How do you get the belt off and what governs the tension?

I can't figure this out, one belts goes from the crank to the compressor, and the other from the crank to the water pump and alternator. Theres no other pullys or tensioner. How do you get the belt off and what governs the tension?
your alternator also acts as a tensioner.. loosen it and slide it toward the engine and whalla.