how do I solve systems by elimination?

THREE questions so let us refer to them as 1. , 2.. and 3.

1.
3x + 4y = 22
-3x + 15y = 111________ADD

19y = 133
y = 7

3x + 28 = 22
3x = - 6
x = - 2

x = - 2 , y = 7

2.
2x - 5y = - 19
3x + 2y = 0

4x - 10y = - 38
15x + 10y = 0________ADD

19x = - 38
x = - 2

10y = 30
y = 3

x = - 2 , y = 3

3.
Equations are identical

1).
3x + 4y = 22
x - 5y = -37
19x = 110 - 148
x = -2
y = 7

2).
-5y = -2x - 19
3x = -2y
2x - 5y = -19
3x + 2y = 0
19x = -38
x = -2
y = 3

3).
-y = -2x- 1
4x = 2y - 2
2x - y = -1
4x - 2y = -2
Both equations are the same.