Will 7.5 16inch pegasus alloy wheels fit an Audi a3 tire number 2055516?

Okay, the "tyre number" is 205 55 16 (not 2055516). 205mm wide, 112.75mm from wheel to tread (55% of 205) and the center is 16" wide for wheels. So yes, 16" wheels will fit on your Audi a3 and they will fit inside your 205 55 16 tires.