Given the sum and difference of two numbers, find these two numbers.

Formula: sum plus difference, the bigger it becomes; Divided by 2, it is big; And subtract the difference, the smaller the reduction; Divided by 2, it is small.

2. Difference ratio problem

Formula: I am more than you, and multiple is cause and effect. Actual difference of numerator, multiple difference of denominator. Double the quotient and multiply it by their respective multiples to get two numbers.

3. Age problem

Formula: the age difference is constant, and it is added and subtracted at the same time. With the change of age, the multiple is also changing. Grasp these three points and everything will be easy.

4. Sum ratio problem

Given the whole, find the part.

Formula: Family members want everyone to be together, and there are principles for separation. Denominator ratio sum, numerator's own. And multiply by the ratio, you deserve it.

5. The problem that chickens and rabbits are in the same cage

Formula: Suppose all chickens, suppose all rabbits. How many feet are there? How many feet are missing? Divided by the foot difference, it is the number of chickens and rabbits.