Almost all of them can: “7 = [ ] + 3” where you write 4 in the box is a standard problem when learning to add, in nearly every workbook. We unteach that skill

Almost all of them can: “7 = [ ] + 3” where you write 4 in the box is a standard problem when learning to add, in nearly every workbook. We unteach that skill between early elementary school and middle school through poor pedagogy.