The four formulas of 5 and 5 are 5+5= 10 and 5-5=0. A figure four formula refers to writing two addition formulas and two subtraction formulas according to 5 and 5. Because these two numbers are the same, there are only two formulas. Addition is one of the four basic operations, which refers to the calculation of combining two or more numbers and quantities into one number and quantity. The addition symbol is the plus sign (+). Connect items with a plus sign when adding. Four operations refer to four operations: addition, subtraction, multiplication and division. Four operations are the important content of primary school mathematics and the basis of learning other related knowledge.