Here are some handy ways to do my math:

• in a Terminal, I could alias ca='printf "%d\n"', then just type ca 3*12-32 to get myself the result, but remember not to have spaces.
• in Vim, under insert-mode, I could use the <c-r>=3*12-32 to directly insert the result.
• Not to mention the Interpreter of many language, like Python and Ruby.