fix another doctest

Author: fchapoton

src/doc/en/prep/Quickstarts/Linear-Algebra.rst

@@ -324,16 +324,16 @@ We can easily solve linear equations using the backslash, like in Matlab.
 ::
 
     sage: A = random_matrix(QQ, 3, algorithm='unimodular')
-    sage: v = vector([2,3,1])
-    sage: A,v  # random
+    sage: v = vector([2, 3, 1])
+    sage: A, v  # random
     (
     [ 0 -1  1]
     [-1 -1 -1]
     [ 0  2  2], (2, 3, 1)
     )
-    sage: x=A\v; x  # random
+    sage: x = A.solve_right(v); x  # random
     (-7/2, -3/4, 5/4)
-    sage: A*x  # random
+    sage: A * x  # random
     (2, 3, 1)
 
 For *lots* more (concise) information, see the Sage `Linear Algebra