Answer:
Not proportional.
Explanation:
We have been given that Nate has 100 bananas. He will eat 2 of them every day.
Let x represent number of days. So bananas eaten in x days would be 
 .
. 
Total number of bananas, y, left after x days would be 

We know that two proportional quantities are in form 
 , where, k is constant of proportionality.
, where, k is constant of proportionality.
Since our equation is not in form 
 , therefore, number of bananas Nate has left is not proportional to the number of days that pass.
, therefore, number of bananas Nate has left is not proportional to the number of days that pass.