Final answer:
The error of recording $48 instead of $84 would result in a $36 addition to the books on the bank reconciliation to account for the under-recorded disbursement.
Step-by-step explanation:
If a bookkeeper mistakenly recorded a disbursement of $48 instead of the correct amount of $84, the error would be shown on the bank reconciliation as a $36 addition to the books. This is because the bookkeeper has recorded less money as being paid out than they should have. Therefore, to correct this, the amount recorded in the books needs to be increased to match the actual disbursement of $84.