I have an old TI-89 calculator and it has the ability to use a variable in a formula and then assign it at the end in one line:

x+12|x=5                        17

But I never could quite figure out how to use multiple variables at once without storing them ahead of time:

5->x
12->y
x+y                             17

But I want to do this on one line without having to save the variables. The solution is to use the "and" keyword.

x+y|x=5 and y=12              17

The most annoying thing about this though is the only way I know of to add the "and" keyword is to look it up in the Catalog menu.