For the checking account:
Let set x for each week when Ellis withdrew.
The initial balance is $1,113.50
and he withdrew $50 from this account.
Then, we can write the next equation:
C=1,113.50-50x
For the saving account:
Let set x for each week when Ellis deposited.
The initial balance is $200.25
and he deposited $20.25 each week.
Then, we can write the next equation:
S=200.25+20.25x
Currently, both accounts are equal. Therefore, we can equal both equations and find the x value to know where both accounts were opened.
Then:
C = S
1,113.50-50x = 200.25+20.25x
Solve for x:
1,113.50-200.25=25x+50x
913.25= 75x
x = 12.17
12.17=x