Another way to do the quiz. I'd appreciate feedback.

/* The function createList creates a list item with the answered question and appends it to the specified list */
function createList(list, question) {
  let listItem = document.createElement('li');
  listItem.textContent = question;
  list.appendChild(listItem);
}

let questions = [
  ['How much is 3 * 9?', '27'],
  ['What is the name of the function that removes the last item in an array?', 'pop'],
  ['What is 2 + 2?', '4']
];


let correctAnswersHeading = document.createElement('h2');
let wrongAnswersHeading = document.createElement('h2');
let listOfCorrectAnswers = document.createElement('ol');
let listOfWrongAnswers = document.createElement('ol');
let outputDiv = document.querySelector('#output');

/* The for of loop iterates through the array and stores each item in the question variable */
/*In this case the question variable holds an array of the question and its answer*/
for (let question of questions) {
  let answer;
  /* If we keep giving no answer we will be prompted to answer again */
  do {
    answer = prompt(question[0]);

    if (answer === '') { alert('You have to give an answer! Try again'); }

  } while (answer === '');

  /* If we answer correct we call the createList function 
     with the list that will hold the correct answers and 
     the question that we answered correctly

     If not we call again the createList but this time with 
     the list of wrong answers.
  */

  if (answer.toLowerCase() === question[1]) {
        createList(listOfCorrectAnswers, question[0]);
  } else {
        createList(listOfWrongAnswers, question[0]);
  }

}

correctAnswersHeading.textContent = listOfCorrectAnswers.childElementCount > 0 ? `${listOfCorrectAnswers.childElementCount} out of ${questions.length} answers were correct. Below are the questions that you answered correctly` : 'You have no correct answers';

wrongAnswersHeading.textContent =  listOfWrongAnswers.childElementCount > 0 ? `${listOfWrongAnswers.childElementCount} out of ${questions.length} answers were wrong. Below are the questions that you did't give the correct answer` : 'You did not make a mistake. Well done.';


outputDiv.append(correctAnswersHeading, listOfCorrectAnswers, wrongAnswersHeading, listOfWrongAnswers);