Sales and Purchases

The following entries appeared in the receivable ledger control account for June. Balance b/f 1st
June is $7,500, sales $20,000, receipts from customers $8,000, irrecoverable debts written off $900.

May I know how to solve this?

This is how I did it, but I am unsure if I am right::

Dr Side:

Bal b/f – $ 7500
Sales – $ 20,000

Cr Side:

Receipts: $ 8000
Irrecoverable Debts: $ 900

Hence,

Bal b/f ($7,500) + Sales ($20,00) = $ 27,500 – Receipts ($8,000) – Irrecoverable Debts ($900) = 18,600

Is this correct?