Answer:
(a) 121 miles
(b) 7 days
Step-by-step explanation:
Given function:
[tex]\sf L(d)=205-7d[/tex]
Question (a)
When d = 12:
[tex]\sf \implies L(12)=205-7(12)[/tex]
[tex]\sf =205-84[/tex]
[tex]\sf =121 \ miles[/tex]
Therefore, the crew has 121 miles left to pave after 12 days.
Question (b)
When L(d) = 156
[tex]\sf \implies 156=205-7d[/tex]
[tex]\sf \implies 7d=205-156[/tex]
[tex]\sf \implies 7d=49[/tex]
[tex]\sf \implies d=\pm\sqrt{49}[/tex]
[tex]\sf \implies d=\pm7[/tex]
As distance is positive, [tex]\sf d=7[/tex] only
Therefore, the crew has been paving the the road for 7 days.
