Explanation:
It is given that,
Sam opened a savings account with a deposit of $50. Every month after that, he deposited $20 more.
It is not a proportional relationship. As initial amount was $50 and every month he deposited $20 more. The ratio is not constant for the deposited amounts.
To make the relationship proportional, he must start with zero balance and then should have deposited $20 every month.