Answer:
300-15d = m
Step-by-step explanation:
Since he spends 15 each day, we dont know how many days, so we put 15d to represent $15 spent each day (d)
We use this formula above ^ and subtract that from 300, which is why it's
300 - 15d
Lastly, we need to find money remaining, so 300 - 15d = m