<E>./test.tex:7: Missing $ inserted.<inserted text> 
                $
l.7 ?
      
I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.<R>
<E>./test.tex:7: Extra }, or forgotten $.\maththreesuperior ->{^3}
                         
l.7 ?
      
I've deleted a group-closing symbol because it seems to be
spurious, as in `$x}$'. But perhaps the } is legitimate and
you forgot something else, as in `\hbox{$x}'. In such cases
the way to recover is to insert both the forgotten and the
deleted material, e.g., by typing `I$}'.<R>
<E>./test.tex:8: Missing $ inserted.<inserted text> 
                $
l.8 
    
I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.<R>