Steven's bank balance is currently R50. What will it be after a. A deposit of R100? b. A withdrawal of R100?

The bank balance of a person is the amount of money available in the bank. This amount increases when we add to our bank account in the form of deposits and it decreases when we remove the money from the bank account through withdrawals. 

The current account balance of Steven is R50. 

a) When a deposit of R100 is made to Steven's account, his bank balance increases by this amount (R100). The new bank balance will be R150 (= R50 + R100).

b) When a withdrawl of R100 is done, one of the two may happen, depending on the bank's policy. Since the total amount in the bank account is only R50, a withdrawal of R100 is not possible. The bank may turn it down, leaving the bank balance as R50. In case, the bank allows partial withdrawal, then the amount from the account (R50) would be withdrawn, leaving the account outstanding by R50.

Hope this helps.