Question 923359
Think of this as one train standing still and 
the other moving at the sum of their speeds
Let {{{ t }}} = time in hrs until they meet
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{{{ 240 = ( 35 + 45 )*t }}}
{{{ 240 = 80t }}}
{{{ t = 3 }}}
They will meet in 3 hrs at 6 PM
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check:
{{{ d[1] = 35*3 }}}
{{{ d[1] = 105 }}} mi
and
{{{ d[2] = 45*3 }}}
{{{ d[2] = 135 }}} mi
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{{{ d[1] + d[2] = 240 }}}
{{{ 105 + 135 = 240 }}}
{{{ 240 = 240 }}}
OK