Question 763467
Carl's speed = x
Rob's speed = x + 6
Carl's time = 156 miles/x
Rob's time = 174/x + 6
As the time were the same
we can say:-
156/x = 174/x + 6
Cross multiply
174(x) = 156(x + 6)
174x = 156x + 936
174x - 156x = 936
        18x = 936
          x = 936/18
          x = 52 mph
Carl's speed = 52 mph
Rob's speed  = 58 mph
Proof:
156/52 = 3hrs
174/58 = 3hrs
Hope this helps.
:-)