You didn’t explicitly state it, but in order for the problem to not be trivial I’ll assume that Braxton and Maggie split their earnings evenly between them. The total income of both individuals is 9x+10+6x+15 = 14x+25. Since Braxton gets to keep half of this, his earnings partnering is (14x+25)/2 = 7x + 12.5. After 5 hours as a team, he makes 7(5)+12.5=47.5 dollars. Alone, he makes 9(5)+10=55 dollars. This means he makes more money alone with a 5 hour timeframe.