# mathbb not recognized however mathcal works! [closed]

I get the following error

Writing index file thessamp.idx ) (./thessamp.aux)
[0{/usr/local/texlive/2011/texmf-var/fonts/map/pdftex/updmap
/pdftex.map}]
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/omscmr.fd)
./thessamp.tex:115: Missing } inserted. <inserted text>
} l.115 $\mathbb{Z} \stackrel{\equiv }$
The set of integers \\ ?


I am using a template from my school, and also, when I try to include the package amsmath, it tells me

./thessamp.tex:7: LaTeX Error: \usepackage before \documentclass.

See the LaTeX manual or LaTeX Companion for explanation. Type  H
<return>  for immediate help.  ...

l.7 \usepackage{
amsmath} ?


I am guessing this is because the style is old or something .. so my question is HOW DO I USE THE mathbb to get me stuff like $\mathbb{Z}$

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## closed as unclear what you're asking by Torbjørn T., Christian Hupfer, Claudio Fiandrino, Ian Thompson, percusseJun 7 '14 at 12:33

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

Welcome to TeX.SX! Please help us to help you and add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with \documentclass{...} and ending with \end{document}. –  yo' Mar 28 '14 at 10:51
You haven't shown any code but presumably the error message means what it says, and you have used \usepackage before \documentclass when it is supposed to be used after it. –  David Carlisle Mar 28 '14 at 11:00
Could you please post a link to that template? –  Malipivo Mar 28 '14 at 11:20
The first error is not caused by \mathbb, but probably by \stackrel which takes two mandatory arguments. I guess you want \stackrel{a}{\equiv} (replacing a with something else). –  Torbjørn T. Mar 28 '14 at 12:32
In addition to the other comments, \mathcal is built in to LaTeX, \mathbb is provided by the amssymb package, not amsmath. –  Andrew Swann Mar 28 '14 at 14:22