Obviously it's 10......25 to 24 is 1 less, 24 to 22 is 2 less, 22 to 19 is 3 less, 19 to 15 is 4 less, so, 15 to 10 would be 5 less.
What Number Should Come Next In The Series 25,24,22,19,15?
10
10
10
10
10