Answer: 210 advanced tickets were sold. 130 same day tickets were sold.
Step-by-step explanation:
x= advanced tickets y=same day tickets
2x+3y=810 this equation represents the money
x+y=340 this equation represents the total number of tickets
x+y=340
-x   -x
y=-340-x       2x+3(340-x)=810        210+y=340
              2x+1020-3x=810        -210   -210   Â
              -x+1020=810            y=130
                -1020  -1020
                 -x=-210
                 -1   -1
                 x=210       Â
              Â