Answer:
see explanation
Step-by-step explanation:
The diagrams show triangular figures
The first figure has 1 dot
The second has 1 + 2 = 3 dots
The third has 3 + 3 = 6 dots
The fourth has 6 + 4 = 10 dots
Note the pattern is + 2 , + 3, + 4
Thus the fifth pattern is 10 + 5 = 15 dots
