pictured below are stacks of solid cubes. determine the number of cubes in the stack and the number of faces glued together.

Solution
For this case we need to find the number of cubes in the stack given so then we can do this:
The first line present 5 cubes
The second line present 5 cubes
And the last line we got:
10 cubes
Then the total of cubes are:
10 +5+5 = 20 cubes
If we need to find the number of faces we can do the following:
5+ 4+ 4+4 +4 +1 + (5+4+4+4+4+1 ) + (5+4+4+4+4+1 ) + (5+ 4+4+4 +4 )
And solving we got:
22+22+ 22+21= 87