My solution (Feedback)

/*
Random Geo Quiz
*/
alert("Welcome to The Ultimate Quiz, type [y]es or [n]o to answer.");

var correctAnswers = 0;
var firstQuestion = prompt("Is Tokyo located in China?");
  if(firstQuestion.toUpperCase() === "N" || firstQuestion.toUpperCase() === "NO"){
   correctAnswers+=1;
  }
var secondQuestion = prompt("Is Cuba in the Pacific Ocean?");
  if(secondQuestion.toUpperCase() === "N" || secondQuestion.toUpperCase() === "NO"){
   correctAnswers+=1;
  }
var thirdQuestion = prompt("Is Canada in the northern hemisphere?");
  if(thirdQuestion.toUpperCase() === "Y" || thirdQuestion.toUpperCase() === "YES"){
   correctAnswers+=1;
  }
var fourthQuestion = prompt("Is Puerto Rico in the Caribbean Sea?");
  if(fourthQuestion.toUpperCase() === "Y" || fourthQuestion.toUpperCase() === "YES"){
   correctAnswers+=1;
  }
var fifthQuestion = prompt("Is Germany in Asia?");
  if(fifthQuestion.toUpperCase() === "N" || fifthQuestion.toUpperCase() === "NO"){
   correctAnswers+=1;
  }

//Define a trophy for each score
var trophyMaterial;
if(correctAnswers === 5){
  trophyMaterial = "platinum";
}else if(correctAnswers === 4){
  trophyMaterial = "gold";
}else if(correctAnswers === 3){
  trophyMaterial = "silver";
}else if(correctAnswers === 2){
  trophyMaterial = "bronze";
}else if(correctAnswers === 1){
  trophyMaterial = "plastic";
}else{
  trophyMaterial = "none";
}

document.write("<h3>Thanks for playing!</h3>");
if(correctAnswers > 0){
document.write("<h3>You got the " + trophyMaterial + " trophy.</h3>");
}else{
document.write("<h3>You got no trophy, better luck next time.</h3>");
}
document.write("<i>You answered " + correctAnswers + " out of 5 questions correctly.</i>");