Prove that if $X\cap Y=\emptyset$, then $X\cup Y$ has $n+m$ elements.
Prove that if $A$ is a set with $m$ elements, $B$ is a set with $n$ elements, and $A \cap B = \emptyset$, then $A \cup B$ has $m+n$ elements.
I have not used Evolution for long time now and I would like to reset all the settings and start from scratch. How would I be able to do this? I'm sure this is a newbie question, but I can't figure this out. I have tried to follow the advice here:  and here:   But I can not seem to be able to generate any font change. I either get no change or error messages.  Here is the output of one failed attempt to change the font to Times using this command:  \rmfamily \renewcommand{\rmdefault}{ptm}     Apparently I either don't have a correct package installed or...  The output says " Metric (TFM) file not found." but I am not sure where to go from there. How to configure splash screen after plymouth I have configured my splash screen for plymouth - and it works perfectly. I've also configured the display manager (I'm using gdm). In between these two I get a very brief splash screen - a kind of swirl of multi-coloured ubuntu like colours. 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I am sure thats with IF Condition.    sed -rne '/21:25:07/,/21:50:07/ p'  server.log.2015-04-21 &gt; /tmp/filename.log ; du -sh  /tmp/filename.log ;  if [`du -sh  /tmp/filename.log` -gt 0] then gzip /tmp/filename.log ; Light fixture with a switch that has an outlet I hope this explains it better: in this room there is a switch with one set of wires and only the black one went through the hole in it, and another black one in the other hole, and is hooked to the outlet by being wrapped around the screw terminals. The ground is cut short and not grounded.  Now on to the outlet: the wire from the switch is connected to the top screw - but it's on the side that says "white".   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Deserialize JSON object into dynamic object using Json.net Financial requirements to sponsor relatives visiting the Schengen area [Germany]?