Final answer:
The average change in Joseph's account during each transaction is -$100.
Step-by-step explanation:
The numeric equation using negatives to show the average change in Joseph's account during each transaction can be calculated by dividing the total withdrawal of $700 by the number of transactions, which is 7. Since the withdrawals represent a decrease in Joseph's account balance, we use negative values. Therefore, the equation is:
-700 ÷ 7 = -100
This equation shows that Joseph's account balance decreased by an average of $100 during each transaction.