how do you find the wet bulb depression if they don't give any other info.

3 answers

Google 'how to find wet bulb depression' and click the 7th link. Sorry, you cannot post links here
I googled Roberta's suggested and you getthis page. Pick out the one that helps.
http://www.google.com/search?q=wet+bulb+depression&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
Link:

theweatherprediction.c0m/habyhints/170/

change c0m to com