Unit 1: Four arithmetic knowledge points 1: In the formula without brackets, if there is only addition and subtraction, it is calculated from left to right in turn. Knowledge point 2: in the formula without brackets, if there is only multiplication and division, it is calculated from left to right in order. Summary: the same level operation is calculated from left to right (that is, addition, subtraction, multiplication and division are the same level). Knowledge point 3: in inclusion ...