Marian had a balance of $102
Then she made two deposits, one of $75 and the other for $50
We can calculate the balance of her checking account after the deposits were done
New balance = $102 + $75 + $50 = $227
The account needs to have at least $300 to avoid a service fee, so we calculate how much is needed to complete that amount
New deposit = $300 - $227 = $73
So, if Marian deposits at least $73, the account balance will be $300 or more
Answer: She must deposit at least $73