fix logical bug at subtract instance method

src/main/java/Rational/Rational.java

@@ -53,7 +53,7 @@ public class Rational {
 
     // COMPLETED - Instance method - this - other
     public Rational subtract(Rational other) {
-        int newNumerator = (this.numerator * other.denominator - other.denominator * this.denominator);
+        int newNumerator = (this.numerator * other.denominator - other.numerator * this.denominator);
         int newDenominator = this.denominator * other.denominator;
 
         Rational result = new Rational(newNumerator, newDenominator);