Answer:
450
Step-by-step explanation:
The total number of possible working groups of 4 workers selecting from 12 workers is the number of ways of selecting 4 persons from 12 persons
[tex]=\binom{12}{4}=\frac{12\times 11 \times 10 \times 9}{1\times 2 \times 3\times 4}=495[/tex]
The total number of possible groups of 4 workers in which 2 persons (Hugo and Viviana) always come together
[tex]= \binom {12-2}{4-2}=\binom {10}{2}=\frac{10\times9}{1\times2}=45[/tex]
So, the total number of possible working groups in which Hugo and Viviana are not working together in any of the groups [tex]= 495-45=450[/tex].