Towards math haters.
(i am one of those)
Just place Instances of an Object outside screen to represent the "possible places".
Lets say: I want a random number between 0 and 10 step 2.
That are the numbers 0, 2, 4 ,6 , 8 and 10.
IN this .cap i place on object with its X on the possible numbers.
Placing those using the "array past" only takes like 4 seconds of your time. download/file.php?id=62
Now just randomly pick one of the objects, and use its X for the random number you need.
And ! this is truly random.
Or take this . cap download/file.php?id=63
Where i used the "array past" to place objects outside screen, to present possible places on the screen by a step of 10.
Just pick a random object for the X, a random for the Y, and feed this to an object that you want to appear on the screen by a 10 * 10 grid.
Or take this .cap download/file.php?id=64
We need to create objects on random places on the screen. But grid related and on empty places.
Just use the "array paste" to create the possible places, marked by an object.
Pick a random of one of those objects. Create the object on that point.
And destroy the place as possible place, by destroying the object marking the place.
Math is a big help, but its not every thing. : )