Question 280060
It's the same problem if you think of 1 train 
as being stationary, and the other moving at
their added speeds
In {{{6}}} hrs:
{{{540 = r*6}}}
{{{r = 90}}} km/hr is their added speeds
Their speeds are {{{r[1]}}} and {{{r[2] = r[1] + 10}}}
{{{r[1] + r[1] + 10 = 90}}}
{{{2r[1] = 80}}}
{{{r[1] = 40}}}
{{{r[1] + 10 = 50}}}
In {{{6}}} hrs, 1st train goes
{{{d[1] = 40*6}}}
{{{d[1] = 240}}} km
and the 2nd train goes
{{{d[2] = 50*6}}}
{{{d[2] = 300}}} km
check:
{{{240 + 300 = 540}}}
OK