Answer:
15
Explanation:
Just find out the pattern. It is decreasing, so let's find out how much it is decreasing by.
31-29= -2
29-24= -5
24-22= -2
22-17= -5
The pattern is -2, -5, -2, -5... So the next one should be -2 again! 17-2=15.
Remember, a pattern doesn't always have to be subtracting, adding, dividing, or multiplying at a constant number! It can switch between two, like this problem!