(a) Setting A(w)=458, we get:
[tex]800-18w=458.[/tex]
Subtracting 800 from the above equation we get:
[tex]\begin{gathered} 800-18w-800=458-800, \\ -18w=-342. \end{gathered}[/tex]
Dividing the above equation by -18 we get:
[tex]\begin{gathered} \frac{-18w}{-18}=\frac{-342}{-18}, \\ w=19. \end{gathered}[/tex]
Therefore Omar has been saving for 19 weeks.
(b) Recall that to evaluate a function at a given value, we substitute the variable by the given value.
Evaluating A(w) at w=5 we get:
[tex]A(5)=800-18\cdot5.[/tex]
Simplifying the above result we get:
[tex]\begin{gathered} A(5)=800-90 \\ =710. \end{gathered}[/tex]
Answer:
(a) 19.
(b) $710.
