Solution:Let's take option 1- Integers are closed under addition
For an integer, the closure property says that if we add two integers, the result will always be an integer. For example 2+3=5.
Here 2, 3 and 5 are integers. So integers are closed under addition. Therefore, this statement is correct.
Now let's take option 2 - Integers closed by multiplication
The closure property of multiplication says that if we multiply two integers, we get an integer in the product. For example, 30×2=60
Here, 30, 2, and 60 are integers. So integers are closed by multiplication. Therefore, this statement is correct.
Now let's take option 3 - Integers closed by subtraction
The closure property of integers states that when two integers are subtracted, the result need not always be an integer. For example- 2−3=−1.
Here, −1 is not an integer. So integers are not closed by subtraction. So this statement is incorrect and option 4 is correct.
So we get that only option 3 is an incorrect statement.