This break-even case is a little more complicated because you need to deal with adults and children at different prices. It is necessary to estimate the ratio of children to adults. In this case the ratio is 1 child to every 2 adults. Cell B15 has a formula which muliplies cell B14 by 2.

Other data you need is:

Total Fixed Costs= 20,000, Variable Cost per Participant= 2.00

Ticket Price for accompanied children= 5, Ticket Price for adults= 20

Formulae have been inserted into a number cells ready for you to make your task easier. You just need to enter appropriate data into the YELLOW cells. Then by trial an error find out what number goes into the BLUE CELL to make the profit closest to zero. You will the have the number of participants needed for the event to break -even, in the right ratio of children and adults.