The first concept you want to remember with this problem is order of operation.
So, first step is to add 3+6 = 9
Next, to get x by itself we would multiply 9 on both sides
( 5x /9) 9 = 9 (1/4)
So, 5x = 9/4
Next, divide both sides by 5 to cancel that out
5x/ 5 = (9/4)/ 5
Next multiply (9/4)/5 × 5/1 because a fraction cannot be divided again so we multiply the denominator by its reciprocal to get rid of it and what we do at the bottom we have to do on top.
So we have x = 45/4
If you have any other questions let me know