Question 1022990
 {{{ 15 }}} = number of people renting bus
Let {{{ c }}} = the flat -rate cost to rent bus
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{{{ c/( 15 + 9 ) = c/15 - 4.5 }}}
{{{ c/24 = c/15 - 4.5 }}}
Multiply both sides by {{{ 24*15 }}}
{{{ 15c  = 24c  - 4.5*15*24 }}}
{{{ 9c = 1620 }}}
{{{ c = 180 }}}
It costs $180 to rent the bus
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check:
{{{ c/( 15 + 9 ) = c/15 - 4.5 }}}
{{{ 180/( 15 + 9 ) = 180/15 - 4.5 }}}
{{{ 180/24 = 180/15 - 4.5 }}}
{{{ 7.5 = 12 - 4.5 }}}
{{{ 7.5 = 7.5 }}}
OK