HP 30b - Business Professional Calculator Quick Start Manual page 19

One way to calculate this problem is to key in the numbers and operations
within the parentheses first, followed by the operation outside of the
parentheses. See Table 1-2.
Table 1-2
Keys
3I
4+
5I
6+
*
Display and Description
Inputs the numbers and the operation in the first set of
parentheses. Intermediate results are displayed. Note the
(+) and (RPN) annunciators.
Inputs the numbers and the operation in the second set of
parentheses. Intermediate results are displayed. Note
the (+) annunciator.
Finishes the operation and displays the results.
Getting Started 13