Calculating the addition and subtraction of fractions with the same denominator means adding and subtracting molecules, and the denominator remains the same; The calculation result can be simplified to the simplest fraction.

To calculate the addition and subtraction of fractions with different denominators, first divide the fraction by the number whose mother is the least common multiple of different denominators in the formula, and then calculate according to the addition and subtraction of fractions with the same denominator.