Answer:
On January 1, 2015, Robert invested $50,000 in his business. 
Date Account Debit Credit 
January 1, 2015 Cash 
 50,000 
January 1, 2015 Cash 
50,000 
On January 4, 2015, Robert bought a laptop for $2,800 for business use. 
Date Account Debit Credit 
January 4, 2015 Office Computer 
2,800 
January 4, 2015 Cash 
2,800 
On January 20, 2015, Robert received $13,000 for services rendered. 
Date Account Debit Credit 
January 20, 2015 Cash 
13,000 
January 20, 2015 Revenue 
13,000 
On January 23, 2015, Robert paid salaries to his staff for $3,500. 
Date Account Debit Credit 
January 23, 2015 Salaries 
3,500 
January 23, 2015 Cash 
3,500 
Step-by-step explanation: