SOLUTION: A cattle train left Abuja and traveled toward the outer-most station. A diesel train left 13 hours later traveling 65 km/h faster in an effort to catch up to it. After three hours

              SPEED          TIME          DISTANCE

CATTLE          r              16            d

DIESEL         r+65           3               d

DIFFERENCE                    13

Let x be the cattle train average speed (the value under the question.


Then the diesel train speed is (x+65) km/h, according to the condition.


The cattle train was on the way for 13+3 = 16 hours and covered the distance of 16*x kilometers


The diesel train was on the way for 3 hours and covered the distance of 3*(x+65) kilometers.


The distance is the same, which gives you an equation


3*(x+65) = 16*x   kilometers.


3x + 3*65 =  16x


3*65 = 16x - 3x


3*65 = 13x  ====>  x =  = 3*5 = 15.


Answer.  The cattle train average speed was  15 km/h.