.
Your equation is:
Dusty distance = Ruth distance
72*t = 60*(t+1), <<<---=== t is time after Dusty' start.
72t = 60t + 60
12t = 60 ====> t = = 5 hours.
Answer. Dusty traveled 5 hours.
Another way to solve the problem :
When Dusty started, Ruth was 60 miles ahead.
But Dusty, having his speed by 12 miles faster than Ruth, decreased the distance between them by 12 miles each hour.
So, in 5 = hours Dusty will catch Ruth.
Solved // by two different ways.
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