HP -67 Owner's Handbook Manual page 41

Getting Started 37
You work through the problem the same way with the HP-67. First
you solve for the intermediate result of (2 + 3)....
Press Display
Intermediate result.
Then add 4 and 5:
(Since you must now key in another pair of numbers before you can
perform a function, you use the EfiZilJ key again to separate thefirst
number of the pair from the second.)
Procedure Press Display
;;A;WM 1ENETD 50
9
Then multiply the intermediate answerstogetherforthe final answer:
Procedure Press Display
Notice that you didn't need to write down or key in theintermediate
answers from inside the parentheses before you multiplied—the
HP-67 automatically stacked up the intermediate results inside the
calculator for you and brought them out on a last-in, first-out basis
when it was time to multiply.
No matter how complicated a problem may look, it can always be
reduced to a series of one- and two-number operations. Just work