Need
you are in charge of decorating for the spring dance. you purchase 5 bags of balloons and 2 rolls of crepe paper for $38. you soon realize that this is not enough to decorate the entire gym. on your second trip to the store, you spend $128 on 12 bags of balloons and 14 rolls of crepe paper. assume the sales tax is included in the price.
a) what was the price of a bag of balloons?
b) how much does each roll of crepe paper cost?

Let the price of a bag of balloon=x     and  the price of a roll of crepe paper =y   
5x+2y=38
12x+14y=128
These are the equation you get from the question   
    5x+2y=38
  -5x        -5x         
     2y=38-5x       divide both side by 2           
     y=19-5/2x 
    
    12x+14y=128     plug in the y
   12x+14(19-5/2x)=128
   12x+266-35x=128    
   -23x+266=128
           -266  -266
       -23x=-138      divide both side by -23
           x=6   this will be the price of a bag of balloon 

    5x+2y=38     plug in x
    5(6)+2y=38
     30+2y=38
    -30       -30
        2y=8         divide both side by 2
         y=4          this will be the price of a roll of crepe paper