gistfile1.rbx

class Problem
  attr_reader :x, :y, :op

  def initialize(op, x, y)
    @op = op
    @x  = x
    @y  = y
  end

  def to_s
    "#{x} #{op} #{y}"
  end

  def answer
    x.send(op, y)
  end
end

if RUBY_VERSION < 1.8.7
  class Array
    def choice
      self[ rand(self.size) ]
    end
  end
end

def create_easy_problem
  op = [:+, :-, :*].choice
  x  = (0...10).to_a.choice
  y  = (0...10).to_a.choice
  Problem.new(op, x, y)
end

def difficult_easy_problem
end

result = {
  :good => 0,
  :bad  => 0,
}

100.times do |n|
  puts "!! #{n} !!"  if n % 10 == 0

  problem = create_easy_problem
  print problem, " = " 
  answer = gets.to_i

  break unless answer
  answer = answer.to_i

  if answer == problem.answer
    puts "good"
    result[:good] += 1
  else
    puts "bad"
    result[:bad] += 1
  end
end

pp result