Given:
Saving, S, after w weeks is represent by the equation

To find:
Whether there is a proportional relationship.
Solution:
If y is proportional to x, then


where, k is constant of proportionality.
Here, there is no constant term and (0,0) satisfy this equation.
The given equation is

Here, we have a constant term.
For S=0 and w=0,


Which is not true as
.
Since, there is a constant term 50 and the equation is not true for (0,0), therefore, the given relationship is not proportional relationship.