1, multiply first, then divide and then add and subtract.

2. Fractions should be divided by division first, and the denominator of two fractions should be replaced by the least common multiple of these two numbers, because the upper and lower fractions are equal to the multiplication and division of a number.

3. Multiply numerator and denominator to get common factor. Molecule times numerator, denominator times denominator.

4. When dividing, first reverse one of the two fractions, change the denominator into numerator and denominator, then change the division symbol into multiplication symbol, and then perform the operation.

Percentage application: to calculate the probability is to divide the "number of occurrences" of an event by the "total number of occurrences", which is equal to the number of occurrences+the number of occurrences, and then get a score, and then change the denominator of the score to 100, which is the percentage. Or give you a percentage for you to calculate. If the probability is x%, it is 1.000 x, which is directly used as a fraction operation.

Clockwise: the clock 12 is directly above, 1 is to the right of 12, and1/is to the left of 12, so 12→ 1 is clockwise.