任务环境 \end{task} 错误和数学模式间距错误

Question

MWE 中有 2 个错误我想要解决。

1. 在列举的 #1 问题中，我将答案加粗到等号右侧。但这弄乱了 = 符号后的正确间距。

   $(12)\div 4 = $\boldmath$3$\unboldmath$

2. \task $7x^2-31x-20$ \end{tasks} causes this error:在 \end{tasks} 处发现最后两行代码未关闭 $。

我花了几个小时搜索 tex stack 论坛，但没有成功。

谢谢你！

\documentclass[addpoints,12pt]{exam}

\printanswers
% un-comment to print solutions.
\renewcommand{\solutiontitle}{}
%\usepackage{multirow, tabularx}
%\usepackage[table]{xcolor}
\usepackage{amsmath}
%\usepackage{multicol}
\usepackage{tasks}
\usepackage[a4paper,margin=0.5in,include head]{geometry}
\usepackage{graphicx} % for "\scalebox" macro
\pagestyle{head}
\header{Algebra I Part 1}
       {}
       {10/14/22} 

\newcommand{\pagetop}{

\noindent 
  \fbox{\fbox{\parbox{\dimexpr\textwidth-4\fboxsep-4\fboxrule}{
    \textbf
    \bigskip
    
  }}}
  \bigskip
  \vspace{0.5mm}
}

\settasks{after-item-skip=1em,
          after-skip=2cm,
          label-width=1.5em, %<---------
          item-indent=2em,   %<---------
          label=(\arabic*),
          column-sep=1em     %<----------
          }
% ------------ DOCUMENT STARTS HERE---------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}

%definition for bigskip = 1 line to replace all \bigskip
\def\bigskip{\vskip\bigskipamount}
Write An Algebraic Expression and then evaluate. SHOW ALL WORK!\\
\bigskip
\centering\boldmath\scalebox{1.33}{$a=2$, $b=3$, $m=4$, $n=5$, $x=10$, $y=15$}\unboldmath
\bigskip
\begin{tasks}(2)
% Prob #1
\task the sum of $a$ and $x$ divided by $4$\\
\vspace{2mm}
$(a+x)\div 4$\\
\vspace{2mm}
$(2+10)\div 4$\\
\vspace{2mm}
$(12)\div 4 = $\boldmath$3$\unboldmath$
% Prob #2
\task $p^2-5p-14$
\vspace{5cm}
% Prob #3
\task $x^2-16x-63$
% Prob 4
\task $7x^2-31x-20$
\end{tasks}
\end{document}