Question 597367
First find how many km head start the container
ship has.
{{{d[1] =  15*1.9 = 28.5 }}} km
Let {{{ t }}} = the number of hours the cruise ship needs 
to travel before the vessels are 125.1 km apart.
The container ship also travels for time {{{ t }}}
after it's head start
{{{ d[2] = 12.6t }}} km
{{{ d[3] = 15t }}} km
--------------
{{{ d[1] + d[2] + d[3] = 125.1 }}} km
{{{ 28.5 + 12.6t + 15t = 125.1 }}}
{{{ 12.6t + 15t = 125.1 - 28.5 }}}
{{{ 27.6t = 96.6 }}}
{{{ t = 3.5 }}}
The cruise ship travels for 3.5 hours until the
vessels are 125.1 km apart