When calculating mixed operations, you should usually calculate from left to right. In other words, the left operation is calculated first, and then the right operation is calculated.

Knowledge expansion:

Addition, subtraction, multiplication and division, also known as four operations, is the most basic operation method in mathematics. Addition, subtraction, multiplication and division not only play an important role in daily life, but also in science, engineering, business and other fields.

Addition is the increase of quantity or physical quantity, which refers to the sum of two or more numbers or quantities. For example, we can say that 5 plus 3 equals 8, which is the sum of 5 plus 3. Addition can be used to calculate the sum of two numbers, the sum of multiple numbers or the sum of consecutive numbers.

The law of subtraction is to subtract another number or quantity from one number, which represents the residual quantity after subtraction. For example, we can say that 8 minus 5 equals 3, which means that the remainder after 8 minus 5 is 3. Subtraction can be used to calculate the difference between one number and another, or to subtract a part from a number.

Multiplication is the repeated addition of quantities, or the multiplication of each quantity. For example, we can say that 2 times 3 equals 6, which means that the sum of 2 times 3 times is 6. Multiplication can be used to calculate multiples of each quantity, or to multiply multiple numbers to get a total.

The law of division is to divide a number into equal parts, or the number of each part is equal. For example, we can say that 6 divided by 2 equals 3, which means that after 6 is divided into 2 equal parts, the number of each part is 3. Division can be used to calculate the quotient of dividing one number by another, or the number of each part after dividing a number into equal parts.

Addition, subtraction, multiplication and division are the basic operation methods in mathematics, and they are also important tools for understanding mathematical concepts and solving practical problems. By mastering the operation methods of addition, subtraction, multiplication and division, we can better understand and solve various problems in life and apply them to science, engineering, commerce and other fields.