Answer:
A proportional relationship is something like:
y = k*x
Where k is the constant of proportionality
And a linear relationship is something like:
y = a*x + b
Is easy to see that if:
a = k, and b = 0, this would be a proportional relationship.
Then if we want to have a slope equal to 3, but this must not be a proportional relationship, we must only have b different than 0.
This could be something like:
y = 3*x + 1
The graph of this is: