3/4 / 2/1 = 3/8 —> Division
211/8 * 2/1 = 211/4 —> Multiplication
3/77 - -23/14 = 37/22 —> Subtraction
1/4 + 8/1 = 33/4 —> Addition
5 and 2.4 (decimal fraction) —> Invalid Fraction
5/5 4 (one fraction at a time) —> Invalid Fraction
2/5 and 0 (division by zero) —> throws IllegalArgumentException 4 denominator