30/20 and 19/30 with common denominators

30/20 and 19/30

To find the common denominator; we must get the least common multiple of each denominator.

20: 20, 40, 60
30: 30, 60, 90

The common denominator is 60.
 
We then multiply each denominator a number that will produce 60. Whatever number will be used to multiply the denominator will also be the number used to multiply the numerator.

30/20 * 3/3 = 90/60
19/30 * 2/2 = 38/60

With both fractions having the same denominator, we can use the numerator to evaluate the value of each fraction.

90 is greater than 38. Thus, 90/60 is greater than 38/60.