all are linear eqns since they follow the formula y = mx + c
1) y = 2x +15
2) 2x -4y = 12 can be rewritten as...
4y = 2x -12 =》 y = 1/2 x - 3
3) 2x - 2y = 12 can be rewritten as...
2y = 2x - 12 =》 y = x - 6
4) 3z -4x =18 can b rewritten as...
3z = 4x - 18 =》 z = 4/3 x - 6
