4/127 + 3/65 = (465 + 3127) / (127*65)
= (260 + 381) / 8255
= 641 / 8255

9/1811 - 2/3411 = (93411 - 21811) / (1811*3411)
= (30699 - 3622) / 6174121
= 27077 / 6174121