1, the same number is added and subtracted on both sides of the equation, and the sign of the equation remains unchanged.

2. Both sides of the equation are multiplied and divided by the same non-zero number, and the sign of the equation remains unchanged.

2. The basic nature of the score: the denominator of the score multiplies (divides) the same number that is not 0, and the value of the score remains unchanged.

Three. Addition and subtraction properties of fractions:

1, add and subtract fractions with the same denominator, denominator unchanged, numerator addition and subtraction.

2. Add and subtract fractions with different denominators, and then add and subtract fractions with the same denominator.