How many addition signs should be put between digits of the number 987654321 and where should we put them to get a total of 99?
Hints

Hints:
1) Try putting addition signs between the different numbers.
2) Try this example:
9+8+76+5+4+3+2+1 = ? -> 7 addition signs.
There are two possible answers:
1) 9+8+7+65+4+3+2+1 = 99 -> 7 addition signs.
2) 9+8+7+6+5+43+21 = 99 -> 6 addition signs.