I'm not sure this would be correct. I'm also assuming they are both travelling in the same direction.
Anyway since the distance is in metres it would be better to convert the speed of each car to m/s
62kph = 17.2 m/s
37.5kph = 10.3 m/s
Subtract the 2 speeds to see how much faster the other one is moving.
17.2 = 10.3 = 6.9
Divide distance by 6.9 to find out how long it would take to get to 138 m.
138/6.9 = 20 seconds.
Now just to make sure I multiplied their speeds by the time to find their distance traveled during this interval.
17.2 * 20 = 344m
10.3 * 20 = 206m
Now I subtracted to see if 138m was the difference.
344 - 206 = 138
Therefore in 20 seconds they will be side by side.