Question

Paul has a white and blue shirt he also has two trousers of brown and black how many different outfits

Answer 1

He can make 4 different outfits
Hope this helps!!!

Answer 2

4 outfits
1 outfit each with the white shirt and different trousers: 1 with brown shorts and 1 with black shorts
then 1 outfit each with the blue shirt and different trousers: 1 with brown shorts and 1 with black shorts
to simplify things:
2shirts * 2 pants = 4 outfits