Question 398817
when the 2nd truck left, the 1st truck 
traveled {{{d = 80*1}}}
{{{d = 80}}} km
Let {{{t}}} = time in hours after 2nd truck leaves
and they are {{{150}}} km apart
The second truck travels {{{d[2] = 60t}}}
The 1st truck travels {{{d[1] = 80t}}}
I have to add {{{d + d[1] + d[2] = 150}}} km
{{{80 + 80t + 60t = 150}}}
{{{140t = 70}}}
{{{t = .5}}} hrs
The 1st truck had traveled {{{1 + .5}}} = 1.5 hrs
when they were 150 km apart
check answer:
{{{d[1] = 80t}}}
{{{d[1] = 80*.5}}}
{{{d[1] = 40}}}
and
{{{d[2] =60t}}}
{{{d[2] = 60*.5}}}
{{{d[2] = 30}}}
and
{{{d + d[1] + d[2] = 150}}}
{{{80 + 40 + 30 = 150}}}
{{{150 = 150}}}
OK