Explanation:
Write a subtraction problem involving two positive integers with a negative difference.
1) When you subtract a positive integer from a negative integer, the difference is always negative.
For example :

2) When you subtract a larger positive integer from a smaller integer, the difference is always negative.
For example :

3) When you subtract two negative integers and the first integer (or minuend) is smaller than the second integer (or subtrahend), the difference is negative.
For example :
