program6_spec.rb

require 'rspec'
require 'rspec/its'
require_relative 'task_seven'

RSpec.describe TaskSeven do
  let(:array) { [5, -3, 3, -5, 6, 6, 6, -1, 0, 2] }

  subject { described_class.new array }

  its(:number_elements_after_max) { should eq 3 }
end

task_seven.rb

class TaskSeven
  def initialize array
    @array = array
  end

  def number_elements_after_max
    max_index = 0

    max_value = @array[0]

    @array.each_with_index do |value, index|
      if max_value <= value

        max_value = value
        max_index = index

      end
    end
    @array.count - max_index - 1
  end
end