Question 724829
They are going in the same direction and will at some time reach the same distance.  By 1 hour into gabe's trip, he has traveled 48*1 miles.  


Gabe and his dad will travel according to 1+t for Gabe, and t for his dad.  
Gabe:  {{{48*1+48*t}}}, miles traveled.
Dad:  {{{72*t}}}, miles traveled.
Those distances will be equal when Gabe's dad reaches Gabe.


{{{highlight(48*1+48*t=72*t)}}}, solve for t.


Further steps: Arithmetic.
{{{48=72t-48t}}}
{{{48=(72-48)t}}}
{{{48=24t}}}
{{{highlight(t=2)}}}, hours for Gabe's dad to meet Gabe.