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2013-10-08T10:15:21+00:00
2013-10-08T10:55:00+00:00
13х-63:7+86=90                                                                                                          13х=63:7+90-86                                                                                                          13х=9+4                                                                                                                13х=13                                                                                                                  х=13:13    х=1