This accept values for 2 reports and then calculate weight average by sale revenue of gross profit and cogs of those reports.

parameterized_working_example.rb

# frozen_string_literal: true

Report = Struct.new(:sale_revenue, :gross_profit, :cogs)

def main
  puts '## First report ##'
  puts 'Input revenue: '
  revenue1 = gets.chomp.to_f
  puts 'Input gross profit: '
  gp1 = gets.chomp.to_f
  puts 'Input COGS: '
  cogs1 = gets.chomp.to_f
  puts '## Second report ##'
  puts 'Input revenue: '
  revenue2 = gets.chomp.to_f
  puts 'Input gross profit: '
  gp2 = gets.chomp.to_f
  puts 'Input COGS: '
  cogs2 = gets.chomp.to_f

  # reports = [Report.new(100, 50, 5), Report.new(200, 100, 10)]
  reports = [Report.new(revenue1, gp1, cogs1), Report.new(revenue2, gp2, cogs2)]

  gp = weight_avg_gross_profit reports
  cogs = weight_avg_cogs reports

  puts "Weight avg gross profit = #{gp.round 2}" # 83.33 with the commented result
  puts "Weight avg cogs = #{cogs.round 2}" # 8.33 with the commented result
end

def weight_avg_gross_profit(reports)
  weight_avg(reports, 'gross_profit')
end

def weight_avg_cogs(reports)
  weight_avg(reports, 'cogs')
end

def weight_avg(reports, value)
  total_weight =   reports.reduce(0) { |sum, r| sum + r.sale_revenue }
  sum_prod = reports.reduce(0) do |sum, res|
    sum + (res.send(value) * res.sale_revenue)
  end

  sum_prod / total_weight.to_f
end

main