16.
[tex]S(4) \text{ it's like t=4, so} \Rightarrow S(4)=9\cdot 4-4=36-4=32[/tex]
17.
[tex]S(4)[/tex] determines how many people have swine in 4 days. But we know that [tex]S(4)=32[/tex]. Hence, S(4) determines that in 4 days, there are 32 thousands people, who have swine already.
18.
[tex]S(t)=23 \Rightarrow 23=9t-4 \Rightarrow t=3[/tex]
19.
[tex]S(t)=23[/tex] determines that in t days, there are 23 thousands people who have swine already. Since [tex]t=3[/tex]. [tex]S(t)=23[/tex] determines that in 3 days, there are 23 thousands people who have swine already.
20.
Watch files.
