Question 939925
Let {{{ n }}} = the number of passengers 
who stayed in Phoenix
{{{ 185 - n }}} = the number who 
did not stay in Phoenix
-----------------------------------
{{{ 90x + 120*( 185 - x ) = 21000 }}}
{{{ 90x + 22200 - 120x = 21000 }}}
{{{ -30x = -1200 }}}
{{{ x = 40 }}}
{{{ 185 - x = 145 }}}
40 passengers stayed in Phoenix and 145 continued to Albuquerque
You were correct
-------------------
check:
{{{ 90x + 120*( 185 - x ) = 21000 }}}
{{{ 90*40 + 120*145 = 21000 }}} 
{{{ 3600 + 17400 = 21000 }}}
{{{ 21000 = 21000 }}}
OK