Hamilton's Essentials of Arithmetic: Lower Grades. E-book. Formato PDF Samuel Hamilton   -  Forgotten Books, 2017  - 

The sign means less or minus. 3 — 2=l 3 less 2 equals 1, or 3 minus 2 equals 1. 4. Read: 3 2 3 5. 2 thumbs less 1 thumb are how many thumbs? 6. Tell a number story about 2 pies less 1 pic.