burger.rb

class Burger
	def initialize(name,value)
		@name = name
		@value = value
	end

	def show
		puts("#{@name} = #{@value} yen")
	end

	def value
		return @value
	end

	def value=(v)
		@value = v
	end

	def name
		return @name
	end

	def name=(n)
		@name = n
	end
end

class Side
	def initialize(name, value, size)
		@name = name
		@value = value
		@size = size
	end

	def show
		puts("#{@name}(#{@size}) = #{@value} yen")
	end

	def name
		return @name
	end

	def name=(n)
		@name = n
	end

	def value
		return @value
	end

	def value=(v)
		@value = v
	end
end

class Set
	def initialize(burger)
		@burger = burger
		@side = Side.new("Potato",100,"S")
	end

	def show
		@burger.show
		@side.show
		val = @burger.value + @side.value - 50
		puts("#{@burger.name} Set = #{val} yen")
	end
end

bg = Burger.new("Cheese Burger",120)
set = Set.new(bg)
set.show

すこし手を加えています。