Suppose s and t are directly proportional. If s=14 when t=18, what is s when t=7?
Since s and t are directly proportional, it means if something is done to one of them, it should be done to the other too to get the symmetrical answer.
If that didn't make sense, here's an example:
Say s=3 and t=9
If s is divided by 3, t must also be divided by 3
In the end, s=1 and t=3
Now, see if you can try it for yourself!
I hope this helped