** Using WeBWorK **

You don't give enough of your problem code to really check what you are doing, but compoundProblem isn't designed to do what you are trying to do (you can't have the same answer rules show up in more than one part, as you appear to be doing, or they will count as answers in both parts, and I'm not sure that will be graded correctly even if you do.

Fortunately, the scaffold macros are set up to provide more flexibility, and you can have previous parts open when later parts are being displayed.

Here is an example of what I think you are after:

loadMacros(
  "scaffold.pl",
  "parserPopUp.pl",
  "parserMultiAnswer.pl",
);

Context("Numeric");
Context->strings->are(yes=>{}, no=>{});

Scaffold::Begin(is_open => 'correct_or_first_incorrect');

$a = random(2,5,1);
$b = random(3,7,1);
$x = random(1,5,1);
$y = random(2,6,1);
$c = $a * $x + $b * $y;

$p = PopUp(["?","yes","no"],"yes");

$ma = MultiAnswer($x,$y)->with(
  checker => sub {
    my ($C, $S) = @_;
    my ($x, $y) = @$S;
    return $a * $x + $b * $y == $c && $x == int($x) && $y == int($y);
  }
);

Section::Begin("Part 1: The Equation");

BEGIN_TEXT
Does the following Diophantine equation have integer solutions?
$PAR
\[ $a x + $b y = $c \]
\{ $p->menu \}
END_TEXT

ANS($p->cmp);

Section::End();
    
Section::Begin("Part 2: The Solution");

BEGIN_TEXT
Good! What is one possible solution?
$PAR
\(x\equiv\) \{ $ma->ans_rule(5) \} and \(y\equiv\) \{ $ma->ans_rule(5) \}
END_TEXT

ANS($ma->cmp);

Section::End();
    
Scaffold::End();

You should be able to start with this and modify it to your needs. See the scaffold.pl documentation for details.