classMyMath#when defining a class method start with self.
defself.add(*numbers)
numbers.inject(0){|number,sum| sum += number}enddefself.multiply(*numbers)
numbers.inject(1){|number,product| product *= number }enddefself.difference(num1,num2)(num1-num2).abs
endend#when calling a class method the syntax is ClassName.method_name
puts MyMath.add(3,5,356,23,9)
puts MyMath.add(84,2,42)
puts MyMath.multiply(8,3,5)
puts MyMath.difference(38,32)
puts MyMath.difference(8,38)