diff --git a/11/Solution #11/exercise.txt b/11/Solution #11/exercise.txt
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++ Solve the system of equations
+	2x - 2y + z - w = 7
+	- x + 4y - 5z + 3w = 1
+	x + y - z + w = 4
+	-4x + 2y + z - 2w = 6
+
+Commands:
+=========
+
+eq1: 2*x-2*y+z-w=7;
+eq2: -x + 4*y - 5*z + 3*w = 1;
+eq3: x + y - z + w = 4;
+eq4: -4*x + 2*y + z - 2*w = 6;
+
+linsolve([eq1,eq2,eq3,eq4],[x,y,z,w]);
+
+
+Solution:
+=========
+(%i1) eq1: 2*x-2*y+z-w=7;
+(%o1)                        z - 2 y + 2 x - w = 7
+(%i2) eq2: -x + 4*y - 5*z + 3*w = 1;
+(%o2)                      - 5 z + 4 y - x + 3 w = 1
+(%i3) eq3: x + y - z + w = 4;
+(%o3)                         - z + y + x + w = 4
+(%i4) eq4: -4*x + 2*y + z - 2*w = 6;
+(%o4)                       z + 2 y - 4 x - 2 w = 6
+(%i5) linsolve([eq1,eq2,eq3,eq4],[x,y,z,w]);
+                          116      39        58        69
+(%o5)                [x = ---, y = --, z = - --, w = - --]
+                          21       7         21        7
+(%i6)
+
+
+Link to solution:
+=================
+http://maxima-online.org/?inc=r-762047752
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