3 is perfectly fine to have, most universities only require 3 A Levels.
If you're really unsure about only taking 3, and worried that you didn't do a Business GCSE, it's okay. A Level Business is made to catch everyone up to speed, and everything learnt in GCSE will be re-taught in more detail, so you don't need to have prior knowledge before taking it as an A Level. Business is a pretty easy A Level to have, and as long as you're okay with research, comprehension and common sense, you should be fine.