Question 891054
3/8,-3/5,33/80
4/7,4/5,23/35

divide row 1 by 3/8
1,-24/15,264/240
4/7,4/5,23/35

add  down (-4/7) *row 1 to row 2
1,-8/5,11/10
0,300/175,70/2450

divide row 2 by 12/7
1,-8/5,11/10
0,1,49/2940

We now have the value for the last variable.
We will work our way up and get the other solutions.

add up  (8/5) *row 2 to row 1
1,0,23660/21000
0,1,7/420

final
1,0,169/150 = 1.12666667
0,1,7/420 = 0.16666667e-1
final 

169/150,7/420