Quoted from Electrocute:( (12 - 1) * (12 - 2) * (18 - 3.25) / 1.68) * .91 = 879
Right idea, wrong formula. You did all 3 dimensions for the box, but only divided out the golf ball size along one dimension. Also, the .91 is a maximum fill portion in just one dimension. Might want to revise. I also noted some golf balls a bit above the rim. Lots of variables... how close to optimal is the filling, how thick are the walls, how precise are the dimensions, etc. Makes it all a challenge.