I need to make a trial balance for these transactions, but whats the step before preparing it. I saw how someone got the trial balance, but I don't understand how those numbers are adding up.

P2-4A The trial balance of Avtar Sandhu Co. shown below does not balance. AVTAR SANDHU C0. Trial Balance June 30, 2017 Debit Credit Cash $ 3,340 Accounts Receivable $ 2,812 Supplies 1 ,200 Equipment 2,600 Accounts Payable 3,666 Unearned Service Revenue 1,100 Owner's Capital 8,000 Owner's Drawings 800 Service Revenue 2,480 Salaries and Wages Expense 3,200 Utilities Expense 810 $12,522 $17,486 Each of the listed accounts has a normal balance per the general ledger. An examination of the ledger and journal reveals the following errors. 1. (11-5 Cash received from a customer in payment of its account was debited for $580, and Accounts Receivable was credited for the same amount. The actual collection was for $850. . The purchase of a computer on account for $710 was recorded as a debit to Supplies for $710 and a credit to Accounts Payable for $710. . Services were performed on account for a client for $980. Accounts Receivable was debited for $980, and Service Revenue was credited for $98. . A debit posting to Salaries and Wages Expense of $700 was omitted. . A payment of a balance due for $306 was credited to Cash for $306 and credited to Accounts Payable for $360. . The withdrawal of $600 cash for Sandhu's personal use was debited to Salaries and Wages Expense for $600 and credited to Cash for $600. Instructions Prepare a correct trial balance. (Hint: It helps to prepare the correct journal entry for the transaction described and compare it to the mistake made.) Problems: Set B and Set C 85 Trial balance totals $15,462