Since both the marbles and boxes are identical, the arrangement

order is not considered.

Only combinations of 3 numbers whose total is 9 are to be counted.

$(9,0,0),(8,1,0),(7,2,0),(7,1,1),(6,3,0),(6,2,1),$

$(5,4,0),(5,3,1),(5,2,2),(4,4,1),(4,3,2),(3,3,3)$

There are 12 such combinations.

$\therefore$ The required no. of ways = 12