Answer:
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Step-by-step exExplanation:
Adding third equation to first one,
7
x
+
5
y
+
z
+
x
−
6
y
−
z
=
0
−
18
or
8
x
−
y
=
−
18
.
(
1
)
Adding 2 times of third one to second one,
−
x
+
3
y
+
2
z
+
2
⋅
(
x
−
6
y
−
z
)
=
16
−
2
⋅
18
or
x
−
9
y
=
−
20
(
2
)
Substracting 8 times of
(
2
)
from
(
1
)
,
8
x
−
y
−
8
⋅
(
x
−
9
y
)
=
−
18
−
8
⋅
(
−
20
)
71
y
=
142
, so
y
=
2
Hence,
x
−
9
⋅
2
=
−
20
or
x
−
18
=
−
20
, so
x
=
−
2
Thus,
7
⋅
(
−
2
)
+
5
⋅
2
+
z
=
0
or
z
−
4
=
0
, so
z
=
4Explanation:
Adding third equation to first one,
7
x
+
5
y
+
z
+
x
−
6
y
−
z
=
0
−
18
or
8
x
−
y
=
−
18
.
(
1
)
Adding 2 times of third one to second one,
−
x
+
3
y
+
2
z
+
2
⋅
(
x
−
6
y
−
z
)
=
16
−
2
⋅
18
or
x
−
9
y
=
−
20
(
2
)
Substracting 8 times of
(
2
)
from
(
1
)
,
8
x
−
y
−
8
⋅
(
x
−
9
y
)
=
−
18
−
8
⋅
(
−
20
)
71
y
=
142
, so
y
=
2
Hence,
x
−
9
⋅
2
=
−
20
or
x
−
18
=
−
20
, so
x
=
−
2
Thus,
7
⋅
(
−
2
)
+
5
⋅
2
+
z
=
0
or
z
−
4
=
0
, so
z
=
4planation:
