Final answer:
Use the AVERAGEIF formula function in cell H23 to find the average cost of brass instruments.
Step-by-step explanation:
To find the average cost of brass instruments using the AVERAGEIF formula function in cell H23, you will need a table containing the names of the instruments in the first column and their corresponding costs in the second column. Let's assume that the instruments are listed in column A and their costs are listed in column B. The formula in cell H23 would look like this:
=AVERAGEIF(A:A,"brass",B:B)
This formula will calculate the average of all the costs in the second column that have the value "brass" in the corresponding cell of the first column.