Three laws of age:
1. The age gap between them is constant.
2. The multiple relationship between two people's ages is the amount of change.
As time goes by, both of them have increased in age by the same amount.
The general way to answer the age question is:
Age after a few years = age difference ÷ multiple difference-young age.
A few years ago, age = young age-age difference/multiple difference.
Subtraction formula
1, minuend-subtrahend = difference
2. Difference+negative = negative
3, the minuend-difference = reduction
Subtraction correlation characteristic
1, inverse exchange rate: subtraction is inverse exchange. If a and b are any two numbers, then (a-b)=-(b-a).
2. Anti-association method: subtraction is anti-association. When trying to redefine subtraction, then a-b-c=a-(b+c).