Answer:
The total change in his account is of -$85, that is, a loss of $85
Step-by-step explanation:
We combine these changes. So
On Tuesday, he withdrew $90 from his account, which means that, the total change, initially of $0, is now of -$90.
On Thusday, he deposited $20, which means that the total change of -$90 is now of -$90 + $20 = -$70
On Friday, he wrote a check of $15, removing 15 from his account, which means the total change will be of -$70 -$15 = -$85
