Apostrophes: 's
 When apostrophes is used to form the plural or possessive of a mathematical expression, the punctuation indicator must be used before the apostrophe. If the apostrophe is omitted in print, it must be omitted in braille.
 1's and 2's
 How many 10's are there in 50?
 Insert +'s or ='s to make true sentences.
 1s and 2s
 There are four 4s in 16.
 +s or =s
 When apsotrophes or "s" is attached to a mathematical expression, it becomes part of that expression and must be punctuated mathematically.
 1's, 2's, and 3's.
 1s, 2s, and 3s.
