. . . . "Sum-solving ink"@en . . "Sum-solving ink was a type of ink that presumably helped solve math problems. Luna Lovegood owned a bottle of turquoise sum-solving ink, but someone took it from her and hid it during the 1995-1996 school year, prompting her to post a notice asking for the return of it and several other missing possessions."@en . . "Sum-solving ink"@en . . . . "Sum-solving ink was a type of ink that presumably helped solve math problems. Luna Lovegood owned a bottle of turquoise sum-solving ink, but someone took it from her and hid it during the 1995-1996 school year, prompting her to post a notice asking for the return of it and several other missing possessions."@en . . . . . .