Step-by-step explanation:
Let's name:

1. He has 4 more stamps from Egipto than from Peru:

2. He has 3 fewer stamps from Nigeria than from Egipto.

3. He has 27 stamps from Nigeria:

Substituting eq3 into eq2:

Substituting E into eq1:

So he has:
- 30 stamps from Egypt
- 26 stamps from Peru
- 27 stamps from Nigeria