Question 983419
At first assume there are N friends so each person paid, {{{C[1]=480/N}}}
Now that 2 more people showed up there are N+2 friends and each pays, {{{C[2]=480/(N+2)}}}
So,
{{{C[2]=C[1]-8}}}
{{{480/(N+2)=480/N-8}}}
{{{480N=480(N+2)-8N(N+2)}}}
{{{480N=480N+960-8N^2-16N}}}
{{{8N^2+16N-960=0}}}
{{{N^2+2N-120=0}}}
{{{(N+12)(N-10)=0}}}
Only the positive solution makes sense here,
{{{N-10=0}}}
{{{N=10}}}
So originally there were 10 people, the cost was $48 per person.
When the two additional people came, the cost was $40 per person.
So at the end there were 12 people on the bus.