Given Data:
Cost of the bike is $ 125.
The amount she already has is $ 60.
The amount she saves every week is $ 5.
(a).
The amount to be saved in w weeks will be equal to 5w.
Thus, the required equation can be formed as,
5w+60=125
(b).
The number of weeks can be determined as,
[tex]\begin{gathered} 5w+60=125 \\ 5w=65 \\ w=13 \end{gathered}[/tex]Thus, the required number of weeks is 13.