Answer:
37
Step-by-step explanation:
Since it is a duet performance we have to pair each singing group to another with all the possible groupings available.
The groups available are
3Mezzos
3Sorprano
2Tenor
2Barritones
Pairing them together we have
Mezzos and Sorprano = 3 * 3= 9
Mezzos and Tenor = 3* 2 = 6
Mezzos and Barritone = 3 * 2= 6
Sorprano and Ternor = 3* 2 = 6
Sorprano and Barritone= 3 * 2= 6
Ternor and Barritone= 2* 2= 4
Total = 37.