Random Position Within Specific Area

[Beocro]

I have no idea what I'm doing... I have it like this:

tEnem.x= Math.random()*(2250+310)-310;
    tEnem.y= Math.random()*(1581+30)-30;

The enemies spawn in the exact x y position each time.

Edit: *facepalm* I forgot the underscore in the x, y position. To anyone else who needs help with this:

tEnem._x= Math.random()*(2250+310)-310;
    tEnem._y= Math.random()*(1581+30)-30;