The difference between 2 / 7 and 3 / 8 is that () is different

The difference between 2 / 7 and 3 / 8 is that () is different

If the denominator of 2 / 7 + 3 / 8 is different, it means that the unit of fraction is different

How to calculate the addition and subtraction of different denominators, such as 3 / 2 + 4 / 3

The first step is to make a general score first, and turn it into a score with the same denominator: 3 / 2 + 4 / 3 = (3 * 3) / (2 * 3) + (4 * 2) / (3 * 2) = 9 / 6 + 8 / 6
The second step is to add fractions with the same denominator, keep the denominator unchanged, and add the numerators: 9 / 6 + 8 / 6 = (9 + 8) / 6 = 17 / 6

When the numerator and denominator of 1 / 3 in 1991 are added with (), the score is 1 / 3

Method 1: according to the meaning of the question, the final denominator is three times of the numerator. We can use the method of unknown number X. let a be added at the same time, and the score is 1 / 3. So: 3 (1 + a) = 1991 + a 3 + 3A = 1991 + a 3a-a = 1