Question 812711
First you have to find the 1st car's head start
{{{ d[1] = 45*2 }}}
{{{ d[1] = 90 }}} mi
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Imagine you start a stopwatch when the 2nd car leaves
Let {{{ t }}} = the time in hours on the stopwatch when 
2nd car catches the 1st car
Let {{{ d }}} = the distance in miles that the 2nd car
travels in time {{{ t }}}
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1st car's equation:
{{{ d - 90 = 45t }}}
2nd car's equation:
{{{ d = 60t }}}
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This is 2 equations and 2 unknowns
so it's solvable
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By substitution:
{{{ 60t - 90 = 45t }}}
You can finish