Algebra
posted by Mary Ann on .
A positive integer minus a positive integer is always positive.
This statement is sometimes true. For example, 17 – 5 = 12, but 15 – 20 = –5.
post five other statements about the addition and subtraction of positive and negative integers, and ask whether each is always true, sometimes true, or never true.

If only two numbers are involved,
Let A and B be real, nonzero numbers.
1) (+)A + (+)B = (+) ?
This is always true.
2) ()A + ()B = () ?
This is always true.
3) (+)A  ()B = (+) ?
This is always true.
4) ()A  (+)B = () ?
This is always true.
5) ()A  ()B = (+) ?
This is not always true. For instance,
5  (3) = 2, but 3  (5) = +2.
Hope this helps~ :3