Answer
4, 6, 11
Work Step by Step
Assume 2 becomes the front face when the net is folded into a cube.
1 and 3 will be folded back and will be opposite sides. $1+3=4$
4 will become the back face, opposite the 2 on the front face. $4+2=6$
5 and 6 will become the top and bottom of the cube. $5+6=11$
