Ben is 20 years older than Daniel. Ben and Daniel first met two years ago. Three years ago, Ben was 3 times as old as Daniel. How old is Daniel now?

The first thing to do is identify the unnecessary information (that they met 2 years ago).
From there, let's go back three years ago. We'll call Daniel's age x, and Ben's age will be 3x. Ben's age is also equal to x + 20.
3x = x+ 20
2x = 20
x = 10
Daniel was 10 three years ago, and Ben was 30. Now, Ben is 33.