How do you solve simultaneous equations?

Simultaneous equations have two unknowns, you need to find out one of the unkowns (eg. x) in terms of the other (e.g. y) in order to solve both unknowns. Using these two examples (x and y) we can construct an example question such as: 2x+y = 15, 2y+3x = 6 Then we choose one equation and solve for x in terms of y or y in terms of x: y=15-2x We now know what y is equal to in terms of x so we substitute that back in to the other equation: 2(15-2x) + 3x = 6 And solve for x: 30-4x + 3x = 6 x=24 And then substitute this into either of the original equations to solve for y: 2(24) + y = 15 y=63