Simplified expression for the amount is 10(9m + 50)
Step-by-step explanation:
If the total months that Troy's grandfather has given him money is m, then the number of months that Troy's mother has given him money is m - 4.
⇒ Total amount in account = 700 + 40m + 50(m - 4)
= 700 + 40m + 50m - 200
= 90m + 500 = 10(9m + 50)