Suppose that there are two types of tickets to a show: advance and same-day. the combined cost of one advance ticket and one same-day ticket is $ 70 . for one performance, 30 advance tickets and 15 same-day tickets were sold. the total amount paid for the tickets was $ 1650 . what was the price of each kind of ticket?

X = advance 
y= same day 

x+y=70

30x+15y=1650


  30x+15y=1650    
- x+y=70               (x15) -> 15x+15y=1050

 30x+15y=1650 
-15x+15y=1050

15x=600
x=600/15
x=40

so now u can insert the price of x AKA the price of the advanced ticket to find our the price of the same day ticket. 

x+y=70
so 
 40+ y=70 
y=70-40
y=30

x = advance =40
y= same day =30