Simple Cancellation of Fractions

[getfirefox]

Hello. These might be easy but I've not done this in years. What are these expressions cancelled down? Not homework, I just can't do them.

http://img692.imageshack.us/img692/4849/fractions.png

Thanks very much guys.

[Mark44]

Respectively, 2/a, 1, and -a/b. In the first it is assumed that b is not 0; in the second that neither a nor b is 0; in the third that b is not 0 and that b is not equal to a.

Notice that in the first problem, we can pull out b/b, which is 1. The second is some number over itself, or 1. In the third problem, (a - b)/(b - a) = (a - b)/-(a - b), or -1. These values are with the previously stated restrictions.