Question

At a concert, tickets were sold at $12 , $30 and $50. The sales of $12 tickets made up 25% of the total amout of money collected. The sales of $30 tickets made up of 60% of the total amount . Given that 5 more $12 tickets were sold than the $30 tickets , how many $50 tickets were sold?
The ans is 18 but i don't understand the method in my book

Answer 1

neither do I. But, if the amounts of the tickets are x,y,z, then

12x = (12x+30y+50z)(1/4)
30y = (12x+30y+50z)(3/5)
x = y+5

Clear the fractions and do some substitution, and you will find that z=18