小问题,帮忙解方程

一.
13X-6Y-4Z-1=0 13X- 6Y- 4Z = 1——①
-6X+15Y-4Z-3=0 -6X+15Y- 4Z = 3——②
-4X-4Y+11Z+6=0 -4X- 4Y+11Z =-6——③
①-② 19x- 21y=-2——④
②×11＋③×4 -82x+149y= 9——⑤
④×82＋⑤×19 1109y=7, y=7/1109
y值代入④ 19x-147/1109 = -2
19x= -2 + 147/1109 = -2071/1109
x = -109/1109
x,y值代入① -13*109/1109 - 6*7/1109 -4Z = 1
4Z = -1417/1109 - 42/1109 - 1 = -2568/1109
z=-642/1109
x = -109/1109
y = 7/1109
z = -642/1109

二.
(1/2+1/3+1/4)X-1/4Y=3
13x/12 - y/4 = 3
13x - 3y = 36——①

-1/4X+(1/4+1/10+1/2)Y=3
-x/4 + 17y/20 = 3
-5x + 17y = 60——②
①×17＋②×3 206x=792
x=396/103
x代入② -5*396/103 + 17y = 60
17y = 60 + 5*396/103 = 8160/103
y = 480/103
x = 396/103