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This page contains the following errors:

error on line 67 at column 8: PCDATA invalid Char value 20

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Below is a rendering of the page up to the first error.

Line 67 from the RSS feed:

x + 2y &lt;= 16<br />

HTML from the question:

<DIV CLASS="entry-content">Gegeben ist das lineare Optimierungsproblem<br />
max x + y<br />
x + 2y <= 16<br />
2x + y >= 12<br />
x + 2y >= 2<br />
x, y >= 0<br />

...

From the question displayed:

x + 2y <= 16

2x + y <= 12

x + 2y >= 2

x, y >= 0

Pasted this in Notepad which gives me a strange:

x + 2y <= 16

2x + y **DC4** <= 12

x + 2y >= 2

x, y >= 0

anyone has an idea how to solve this bug for the next occurence?

// RSS feed now works again, I removed "DC4" from the question.