Manuel wants to save $600 to buy a TV. He saves 18 each week. The amount A (in dollars) that he still needs after w weeks is given by the following function.A (w) = 600-18w

(a) Substituting with w = 7 into the equation we get:
[tex]\begin{gathered} A(7)=600-18\cdot7 \\ A(7)=600-126 \\ A(7)=474 \end{gathered}[/tex]He still needs $474
(b) Substituting with A(w) = 294 into the equation we get:
[tex]\begin{gathered} 294=600-18w \\ 294-600=-18w \\ -306=-18w \\ \frac{-306}{-18}=w \\ 17=w \end{gathered}[/tex]He has been saving for 17 weeks.