SOLUTION: The set of whole numbers is closed under subtraction.True or false? The set of integers is closed under multiplication.True or false? The set of integers is closed under division

The whole numbers are {0,1,2,3,...}

False, because you can subtract your way out of the set of whole 
numbers. For instance take the two whole numbers 2 and 5.  If you 
subtract  2 - 5 you get a negative number -3, and no negative numbers 
are whole numbers.  So you've subtracted your way out of the set of 
whole numbers.

True, because you can't multiply your way out of the set of integers.
If you multiply an integer by an integer, you will always get another 
integer.

False, because you can divide your way out of the set of integers.
For instance if you divide the integer 1 by 2 you get , which
is not an integer.  So you've divided your way out of the set of 
integers. 

Edwin