Im wondering where the contribution margin ratio comes from? I get the fixed expenses and operating income but not sure where the percentage is coming from? Thanks for any help!

Luxury Cruiseline offers nightly dinner cruises departing from several cities on the eastern coast of the United States including Charleston, Baltimore, and Alexandria. Dinner cruise tickets sell for $50 per passenger. Luxury Cruiseline's variable cost of providing the dinner is $20 per passenger, and the fixed cost of operating the vessels (depreciation, salaries, docking fees, and other expenses) is $210,000 per month. The company's relevant range extends to 19,000 monthly passengers. Compute the number of dinner cruise tickets Luxury Cruiseline must sell to breakeven and the sales dollars needed to breakeven. Compute the number of dinner cruise tickets Luxury Cruiseline must sell to breakeven. Use the shortcut unit contribution margin approach. First, identify the formula, then compute the breakeven sales in units. (Complete all answer boxes. For amounts with a $0 balance, make sure to enter "0" in the appropriate cell.) + Operating income Fixed expenses 210,000 / 1 $ Contribution margin per unit 30 = Breakeven units 7,000 Compute the sales dollars needed to breakeven. Use the shortcut unit contribution margin ratio approach. First, identify the formula, then compute the breakeven sales in dollars. (Complete all answer boxes. For amounts with a $0 balance, make sure to enter "0" in the appropriate cell. Enter the contribution margin ratio as a whole percent.) Fixed expenses Operating income ) / Contribution margin ratio = Breakeven sales ( $ 210,000 + $ 60% = $ 350,000