I didn't use to have this problem but it seems like | started appearing after math stuff. (I use PGML if that matters.)

I've attached a screenshot of the problem. Here's the

source for the problem....

DOCUMENT();

loadMacros(

"MathObjects.pl",

"PGstandard.pl",

"PGML.pl",

"PGcourse.pl",

"parserNumberWithUnits.pl",

"contextArbitraryString.pl",

"parserMultiAnswer.pl",

"parserPopUp.pl",

"contextInequalities.pl",

"PGgraphmacros.pl",

);

TEXT(beginproblem());

$showPartialCorrectAnswers = 1;

######################################################################

Context("Numeric") ; Context()->flags->set(tolerance => 0.01);

BEGIN_PGML

Calculate [`\int_{-3}^{3} \sqrt{9 - x^2} dx`].

Hint: What is the shape of the corresponding area?

[________________________]{Compute("9*pi/2")}

END_PGML

######################################################################

ENDDOCUMENT();