Subsitution algebra problem?

Question

-3x+3y=4
-x+y=4

-4x+y=6
-5x-y=21

Answer 1

Substitution:

-3x + 3y = 4

-x + y = 4

These lines slopes are equal then the  lines are parallel .

They have no solution.

Answer 2

-4x + y = 6    -(1)

-5x - y = 21  -(2)

Add 5x to each side

- y = 21 + 5x

Substitute y = -5x - 21 in the equation (1)

-4x -5x -21 = 6

-9x -21 = 6

Add 21 to each side

-9x = 6 + 21

x = -3

Substitute x = -3 in the equation(1)

12 + y = 6

y = -6.