how can we determine key words to find what kind of sign to use
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The problem says there are:
2 neighbors with birds
10 neighbors with cats
8 neighbors with dogs.
As each neighbor owns only one pet, the total number of neighbors is then:
2+10+8=20
The percentage of the neighbors that own dogs is the number of neighbors with dogs, divided by the total number of neighbors, then:
[tex]\frac{8}{20}\times100=\frac{4}{10}\times100\text{ \%=0.4x100\%=40\%}[/tex]Then the 40% of the neighborhood pet owners have dogs.