if the fractions are dissimilar, turn dissimilar fractions into similar fractions by finding their lcd (least common denominator). if both are similar, just subtract the numerators like whole numbers but do not subtract denominators.
examples:
similar fractions: 3 - 2 = 1
5 5 5
dissimilar fractions: 2 - 1 -> 4 - 3 = 1
3 2 -> 6 6 6
mixed no.: 1 2 - 4 -> 1 10 - 12 -> 25 - 12 = 13
3 5 -> 15 15 15 15 15
