<PRE><B>Question 970250</B>
Think of this as one of the streetcars standing 
still and the other moving at the sum of their speeds
Let {{{ s }}} = the speed of the slower one
{{{ s + 15 }}} = the speed of the faster one
-------------------------------------
Convert minutes to hrs:
{{{ 12/60 = 1/5 }}} hrs
----------------------
{{{ 11 = ( s + s + 15 )*( 1/5 ) }}}
{{{ 55 = 2s + 15 }}}
{{{ 2s = 40 }}}
{{{ s = 20 }}}
and
{{{ s + 15 = 35 }}}
--------------------
Their speeds are:
20 mi/hr and
35 mi/hr
---------------
check:
{{{ 11 = ( s + s + 15 )*( 1/5 ) }}}
{{{ 11 = 55*( 1/5 ) }}}
{{{ 55 = 55 }}}
OK</PRE>