can someone show me how did my professor come up with the answer please

Assume the following data for Vote, Vote, Vote Your Voice, Inc., a for-profit company, that creates voting simulation modules for elementary and secondary schools, as well as registers college students of all political party affiliations to vote. (S in thousands) 2018 2018 2017 Sales $2,350.0 Cash $ 450.0 $325.0 COGS 1.175.0 Accounts Receivables 895.5 755.5 SGSA 587.5 Inventory 1,375.5 1.265.0 One-time restructuring charge 250.0 Other current assets 410.0 300.0 Op Income 337.5 Current Assets 3,131.0 2,645.5 Interest expense 125.0 PP&E 1,100.0 1,050.0 Pre-tax 212.5 Goodwill Income 525.5. 475.0 Taxes 42.5 Total Assets 4,756.5 4.170.5 Net income $ 170.0 Accounts payable 925.5 850.0 Revolving line of credit 275.0 250.0 Other current liabilities 650.5 600.5 Current Liabilities 1,851.0 1,700.5 Notes Payable 525.0 400.0 Deferred taxes 150.0 125.0 Total Liabilities 2,526.0 2.225.5 Shareholders' Equity 2.230.5. 1,945.0 $4,756.5 $4,170.5 1. Calculate the 2018 Recurring Operating Margin and explain what it means, (6 pts) 25% + explanation