Question 213518
Assume I have a stopwatch and I start it
when the motorboat leaves.
The sailboat has got a headstart of
{{{36*4 = 144}}} mi
When I start the stopwatch, they will both 
travel for the same amount of time, but the motorboat
has to go {{{144}}} mi farther
For the sailboat,
{{{d = 36t}}}
For the motorboat,
{{{d + 144 = 60t}}}
By substitution:
{{{36t + 144 = 60t}}}
{{{24t = 144}}}
{{{t = 6}}} hrs
The motorboat catches the sailboat in 6 hrs
{{{d = 36t}}}
{{{d = 36*6}}}
{{{d = 216}}} mi
This is how far the sailboat goes after I start
the stopwatch. The distance from the harbor is
360 mi 
{{{144 + 216 = 360}}}