Question 468963
Let d=distance, r=rate or speed, and t = time.
d = r*t
The trip there and back are both the same distance of 120mi. 
Therefore using substitution
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{{{120 = x*t}}}
{{{120/x = t}}}
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{{{120 = (x+5)*(t-(1/3))}}}
{{{120/(x+5) = t-(1/3)}}}
{{{(120/(x+5))+(1/3) = t}}}
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Setting the times equal to each other
{{{120/x = (120/(x+5))+(1/3)}}}