To calculate the number of possible different groups of albums she could put, we need to multiply the number of options for each group together.
The number of options for EXO is 2.
The number of options for GOT7 is 4.
The number of options for Red Velvet is 6.
The number of options for SHINee is 3.
To find the total number of possible groups, we multiply these numbers:
2 (EXO) x 4 (GOT7) x 6 (Red Velvet) x 3 (SHINee) = 144
Therefore, there are 144 different possible groups of albums she could put on the shelf.
If she has already decided on the EXO albums, she doesn't have a choice for that group anymore. So, only the other groups are left to be decided.
The number of options for GOT7 is 4.
The number of options for Red Velvet is 6.
The number of options for SHINee is 3.
To find the total number of choices left for the other groups, we multiply these numbers:
4 (GOT7) x 6 (Red Velvet) x 3 (SHINee) = 72
Therefore, there are 72 choices left for the other groups.