I have used a simple formula with subset_sum(value*weight)/ subset_sum(weight), which works well. I presume the easier weighted average is not available in the Content View.
The 'intermediate multiplication' calculation for each pair Xi and Wi should be done in the Table View, creating a new field with formula [Value x]*[Weight w]. The Content View formula will divide sums of two columns. Result will respond to filtering, so you might want to set the Data subset for the Content view to point to 'All values'.