Answer:
Rule: 400 + 25x
After Month 12: 700 dollars
Step-by-step explanation:
To start, we need to set a variable as the amount of months after you started your savings account. Call this value x. Now, we just have 25x as the amount you gain after x months, so the rule is 400 + 25x. To calculate how much you have after month 12, just plug in 12 to get 400 + 300 = 700 dollars.