A charity will give away exactly $600 for tickets for adults and children to attend a concert. The adult tickets are $3.00 each, while each child's ticket costs $2.00. The $600 could be used for 200 adult tickets and no child tickets; it could be used for 300 child tickets and no adult tickets; or some combination of adult and child tickets that adds to a cost of $600; for example, 60 child tickets at a cost of $120 and 160 adult tickets at a cost of $480. However, another restriction exists that limits the number of adult and children tickets: the number of adult tickets must be 200 less than twice the number of child tickets. How many adult tickets and how many child tickets should be purchased to meet these two conditions? .