Answer:
I don't know
Step-by-step explanation:
Unknown, but you could probably use Googl#
Option c
25
The pattern is + 1, + 3, + 6,... i.e. + 1, + (1 + 2), + (1 + 2 + 3),...
.'. Missing number = 15 + (1 + 2 + 3 + 4) = 25.