The mixed operation of addition and subtraction of grades in grade five refers to the addition and subtraction of grades in the calculation process. This kind of operation needs to pay attention to some special skills and laws.

Here are some key points and steps that can help you solve the problem of five-level fractional mixing operation:

First, make sure that all fractions have the same denominator. If the denominators are different, you need to find their common denominators and convert them first. For example, if there are two fractions with denominators of 3 and 4 respectively, their denominators can be changed to 12 to facilitate calculation.

Second, add and subtract, and perform corresponding operations on molecules. Increase or decrease the numerator of the fraction and keep the denominator unchanged.

Third, if possible, simplify the results. Simplify the result to the simplest form, that is, the numerator and denominator are divided by their greatest common divisor.

Fourth, if necessary, convert the results into fractions or mixed numbers. This is a representation that converts the result into an integer and a true fraction. If the numerator is greater than or equal to the denominator, you can take out the integer part and take the rest as the true fraction.

Fifth, check whether the answer is reasonable. It can be verified by estimation or calculator to ensure that the answer is correct in value.

The following is an answer to a sample question:

Question: Calculate the result of the following fractional mixed operation: 3/4+ 1/2- 1/8.

Answer: First, we need to make sure that the denominators of the scores are the same. Convert 3/4 and 1/2 into fractions with denominator of 8, and get 6/8+ 4/8- 1/8.

Then add: 6/8+4/8-1/8 =10/8-1/8.

Then, simplify the result: 10/8- 1/8=9/8.

Finally, we can convert the results into component numbers: 9/8= 1 and 1/8.

Therefore, 3/4+1/2-1/8 =1and1/8.

In a word, learning mathematics requires persistent efforts and hard training. Through reasonable study methods and unremitting efforts, I believe you will get good grades in mathematics.