What are simultaneous equations and how do I solve them?

E.g you have 2 equations and have to set them equal to each other. 
2x + 3y = 6 
-3x +  y = 2

multiply first equation by 3, second by 2 to get
6 x + 9y = 18
-6 x + 2y = 4

11 y = 22

y = 2

-6x + 2(2) = 4

-6x = 0

x = 0