Rectangular solid that is 6-cm-by-6 cm-by-6 cm is painted on all six faces. then the solid is cut into cubes that measure 2 cm on each side. how many cubes have only one face painted?

If you check the picture below

the rectangular solid is a 6x6x6, so all sides are equal thus is a cube

is painted on all faces, so the only part that's painted is the faces, ok
then you split it like in the picture, you have all 6 faces painted there,

now, let's say each of those 6 faces are cut in 2cm

how many of those 2cm pieces will each have?   so get that amount for each and sum them up, that's how many of the cubes have one face painted

only the cubes that are part of the face, which was painted, are the ones that have a painted face themselves

keep in mind that each face is a 6x6 rectangle
notice the 2nd picture below

The answer would be 13.5 minutes.