Question 822522
Writing in matrix form we get the augmented matrix:

{{{
(
 matrix( 4, 5, 
1,1,0,0,140,
0,1,1,0, 160,
0,0,1,1, 130,
1,0,0,1, 110
 )
)
}}}

After row operations the system can be transformed to:

{{{
(
 matrix( 4, 5,
1,0,0,1, 110,
0,1,0,-1,30,
0,0,1,1, 130, 

0,0,0,0,0

 )
)
}}}

using t we can write:



A=110-t
B=t+30
C=130-t
D=t