“latex missing } inserted” error message in equation [closed]

I have a slightly complex, long section of equations in my latex document, but from what I can see I think it is programmed correctly. When I compile the document, I get the error

"./ThesisDraft1.tex:111: Display math should end with . ^ l.111 ...dD}{dt} = \frac{\Gamma \times A}{x$^{2}$}"

The error starts at the first line of the equation, and if I comment out that line, moves to the second line of the equation and crashes, etc. I have tried commenting out the entire equation block and the document compiles with no problem, so I know it's a problem with this equation block. I have another equation earlier in the document, but that compiles with no problem.

Here is the code block:

   \begin{displaymath}
\frac{dD}{dt} = \frac{\Gamma \times A}{x$^{2}$}
dD = \frac{\Gamma \times A}{$x^{2}$}dt
\int{dD} = \int_0^21hrs  \frac{\Gamma \times A}{x$^{2}$}dt
\int{dD} = \frac{\Gamma}{$x^{2}$} \int_0^21hrs A dt = \frac{\Gamma \times A$_{0}$}                       {x$^{2}$} \int_0^21hrs exp$^{-\delta t}$ dt
\end{displaymath}


Any ideas are greatly appreciated!

-

closed as off-topic by cmhughes, ChrisS, dustin, Christian Hupfer, moeweMay 8 at 5:25

• This question does not fall within the scope of TeX, LaTeX or related typesetting systems as defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

remove the $ you are already in math mode – David Carlisle May 8 at 0:46 Welcome to TeX.SE. Also, not sure about the 0^21hrs. Is that intended to be 0^{2} 1hrs, or 0^{21} hrs, or something else? – Peter Grill May 8 at 1:26 Thanks David, that worked! Any idea how I can close out this question? – katrijnn May 8 at 2:21 This question appears to be off-topic because it has been resolved in the comments by removing the superfluous$ –  cmhughes May 8 at 3:51