https://gist.github.com/00b60c92f6ab07112587c1977bd8aceb

Grade-Average with three parameter

// function
const sumOfFinalGrade = (test, homework, exam) => {
  // if (test < 0 || test > 100 || homework < 0 || homework > 100 || exam < 0 || exam > 100){
  //   return 'You have entered an invalid grade.';
  // }
  return test + homework + exam; 
};

// function
const finalGrade = (test, homework, exam) => {
  if (test < 0 || test > 100 || homework < 0 || homework > 100 || exam < 0 || exam > 100){
    return 'You have entered an invalid grade.';
  }
  const average = sumOfFinalGrade(test, homework, exam) / 3;
  if (average <= 59) {
    return 'F'
  } else if (average <= 69) {
    return 'D'
  } else if (average <= 79) {
    return 'C'
  } else if (average <= 89) {
    return 'B'
  } else if (average <= 100) {
    return 'A'
  }
};

// output
console.log(finalGrade(-1, 92, 95)) 

Please i have been Struggling with LINE 3 and 4, i am trying to move Line 3 and 4 to finalGrade function without rewriting the if else statement like i did in Line 11 and 12.. ! Thanks