Observe patterns and look for patterns. Set the pattern as shown in the picture with matches. How many matches does it take to set it to the 20th?

The first picture? A triangle with three matches.

The second picture? 1+2 triangle (1+2)X3? individual match

The third picture? 1+2+3 triangles (1+2+3)X3 match.

According to the equivalence of reasoning

20. Figure 20? 1+2+3 ...+20 triangles? (1+2+3 ...+20) X3 matching

2 1X 10X3=630 match ~ ~