Thank you for the question! I understand the temptation to use the UEB modifier for the tilde over the n; however, UEB symbols may not be used within Nemeth Code (other than the transcriber-defined shape indicator). So, for piñatas you must use the dot 4 that indicates an accent on the following letter, as shown below.
_% #18 kazoos./6 pi@natas .k #3 kazoos per pi@nata _:
Please note that in the above:
the numeric indicator is required before a number that is preceded by a blank cell, and
the equation "18 kazoos ÷ 6 piñatas = 3 kazoos per piñata" will not fit all on one braille line and so must be broken before the symbol of comparison.
I commend you on your decision to include within the Nemeth Code switch indicators the whole expression "18 kazoos ÷ 6 piñatas = 3 kazoos per piñata".