I just noticed that several webwork problems do not display the left/right braces (for sets) in several problems. Here are snippets of the relevant codes (the double quotes are part of the original codes):

"\( $lbrace x \in \mathbb{R} \mid x^2-2=0 $rbrace\)"

"\( $LBRACE x \in \mathbb{Q} \mid x^2-2=0 $RBRACE\)"

"\($LB 3 $RB \) is an element of \($LB $LB 3 $RB $RB\)."

In case this matters, I am using webwork 2.15, and here are the macros used:

loadMacros(

"PGstandard.pl",

"PGunion.pl",

"MathObjects.pl",

"PGcourse.pl",

"parserMultiAnswer.pl",

"PGchoicemacros.pl",

"PG.pl",

"PGbasicmacros.pl",

"PGchoicemacros.pl",

"PGanswermacros.pl",

"unionTables.pl",

);

Many thanks for your help!