Tickets at a football match cost $6,$10 or $15 each. The number of $10 tickets sold was 3 times the number of $6 tickets sold and 500 less than the number of $15 tickets sold. If the total gate receipts were $84450, how many of each type of ticket was sold?
So, what do we know?
If there are x,y,z tickets for 6,10,15 dollars, respectively, then
y = 3x
y = z-500
6x+10y+15z = 84450
Now just solve for x,y,z. (substitution is probably easiest here)