FIRST PERSON 2 ANSWER AND SHOW ALL WORK GETS 10 PTZ?

Sue's, Lucy's and Helen's rates of work are 1/10 job/hour, 1/12 job/hour, and 1/13 job/ hour. Set up the equation for Sue and Lucy if they work together 3 hours and then are joined by Helen. How long will they take to complete the job? please show all work