Please help advanced functions question for me

Jack and Jill work at the same store. Jack's total weekly salary, in dollars, if he sells x items is given by 5= 100 + 5x, and Jill's total weekly salary, in dollars, if she sells x items is given by S = 80 + 6X_ Assuming that they sell the same number of items in a week, what is the minimum number of items they have to sell so that Jill's weekly salary is at least $200 more than Jack's? [4]