When subtracting fractions, the first thing to check is if the denominators are the same.
Subtracting Fractions with Like Denominators
Fractions with the same denominators are called like fractions.
To subtract fractions with like denominators, subtract the numerators , and write the difference over the denominator.
Since the denominators are the same, subtract the numerators.
Subtracting Fractions with Unlike Denominators
If the denominators are not the same, then you have to use equivalent fractions which do have a common denominator . To do this, you need to find the least common multiple (LCM) of the two denominators.
To subtract fractions with unlike denominators, rename the fractions with a common denominator. Then subtract and simplify.
For example, suppose you want to add:
The LCM of and is . So, we need to find fractions equivalent to and which have in the denominator. Multiply the numerator and denominator of by , and multiply the numerator and denominator of by .
Now we have like denominators, and we can subtract as described above.