



 
Hi Heather, The question Stephen solved in the page you reference was
Stephen's solution began
and he arrived at the answer \[y = 2x + 120.\] In this expression if $x = 0,$ that is there are no passengers then the cost is $\$120$ so the cost for an empty bus to use the ferry is $\$120.$ If $x = 1$ then the cost is $120 + 2 = 122$ dollars and if $x = 2$ then the cost is $120 + 4 = 124$ dollars and so on. The number 2 in the equation $y = 2x + 120$ is the additional cost per person in dollars. Thus the "fixed" cost is $\$120,$ fixed because it doesn't depend on the number of passengers and $\$2$ is the additional cost per person. I hope this helps,  


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