X+Y = 1 1Y-X = 5② from ①, x =1y3 to ②, 2y=6 y=3 and y=3 to ①, X+3 = 1X =-2.

The second one:

X+Y = 2 1Y-X = 0② x=y③ from ②，2x = 1X = 1X = 1X = 1X = 65438- 1Y = 1。

The third one:

X-y = 0 12y+x =-6 ② from ① x = y3, ③ instead of ② 3y=-6 y=-2, and y=-2 instead of 1x2 = 0x =-2.

Actually, I am also a junior high school student. I can do it if I am careful.