Substitutions

1. x + 4y = 6

y = - x + 3

2. x + 2y = 6

x - y = 3

1x + 4 (-*+3) = 6

1 * - 4 * + 12 = 6

-3 * = - 6

* = 2

2 * + 2y = 6

* - y = 3

multiply second equation by 2x - 2y = 6

now add equations

4x = 12 so x = 3. substitute 3 - y = 3 so y is 0. check in first equation 2*3 + 2*0 = 6. 6+0 = 6