1. Let the three boxes be box 1, box 2, box 3
consider the 2 white balls, they can be placed in the 3 boxes as follows:
BOX1: BOX2: BOX3:
__2___ ___0__ __0___
__0___ ___2__ ___0__
__0___ ___0__ ___2__
___0__ ___1__ ___1__
__1___ ___0__ ___1__
__1___ ___1__ ___0__
so there are 6 possibilities to place the white balls. Similarly there are 6 ways to place the black balls. We can combine any position of the black balls with any position of the white balls, so there are in total 6*6=36 ways to place the balls.
Answer: 36
