public void calculate(boolean addLetters)
	{
		elements.clear();
		
		if(calculations != null)
		{
			elements = ArithmeticParser.doCalculationInstructions(calculations);
			
			problemHeader = QuizGenerator.replaceVariables(elements,problemHeaderOriginal);
			
			for(Question q : questions)
			{
				q.calculate(elements,addLetters);
			}
		}
	}