Question

one day a toy store sold 3 xylophones and 3 yo-yos for $33. another day it sells 2 xylophones and 1 yo yo for $19. equations for the two days are 3x+3y=33 and 2x+y=19 where x is the value of one xylophone and y is the value of one yo-yo.

Answer 1

3x+3y=33     notice how in the bottom equation you can multiply y by 3 to get 
2x+y=19       what is on top. This sets you up for an easy case of elimination!                                 Multiply everything on the bottom by -3 to start.
3x+3y=33     Then you can cross out the y's (because they're opposite) and 
-6x-3y=-57                             combine equations 

-3x=-24   From there it is pretty straight forward to find x: Just divide -24 by -3

x=8             Then plug it back into any of your original equations and find y

3(8)+3y=33                            You should find that y=3