Analysis: In this transaction, take advantage of Boss Wang's expenditure-income, and the result is what you want.

Answer: Because the total cost is 79+18+100 =197,

The total income is 100+ 100 (counterfeit money) = 100, so 197- 100 = 97.

This problem uses the mixed operation of knowledge points of rational numbers and rational numbers. It does not examine simple calculations, but combines practical problems.

Extended data:

Law of rational number operation

First, the addition algorithm:

1, additive commutative law: Two numbers are added, the position of the addend is exchanged, and the sum is unchanged, that is.

2, the law of addition and association: three numbers are added, the first two numbers are added first or the last two numbers are added first, and the sum is unchanged, that is.

Second, the subtraction algorithm:

Law of subtraction: subtracting a number is equal to adding the reciprocal of this number. Namely:

.

Third, the multiplication algorithm:

1, multiplication and conversion law: when two numbers are multiplied, the position of the exchange factor remains unchanged, that is.

2. Multiplication and association law: when three numbers are multiplied, the first two numbers are multiplied first, or the last two numbers are multiplied first, and the product is unchanged, that is.

3. Multiplication and distribution law: multiplying a number by the sum of two numbers is equivalent to multiplying this number by these two numbers respectively, and then adding the products, namely:

.

Baidu encyclopedia-rational number