First, the basic nature of quotient invariance: the dividend and divisor are multiplied or divided by the same number at the same time, and the quotient remains unchanged.

Secondly, subtraction has the following operational characteristics:

1. A number MINUS a number plus the same number, a number remains the same;

2. If you subtract a number from the sum of n numbers, you can subtract this number from any addend and add it to the rest of the addends, and the result remains unchanged;

3. If you subtract the sum of n numbers from a number, you can subtract each addend in the sum from this number in turn, and the result remains unchanged;

4. If you subtract the difference between two numbers from a number, you can subtract the minuend in the difference from this number and add the minuend in the difference; Or add subtraction in the difference first, and then subtract the minuend in the difference, and the result remains unchanged;

Third, the basic nature of the fraction: the numerator and denominator expand or shrink the same multiple at the same time, and the fractional value remains unchanged.

Fourth, the basic nature of the ratio: the first and second items of the ratio are multiplied by the same number at the same time, and the ratio remains unchanged.