Addition and subtraction facts through 18 build from counting and picture-set addition up to word problems where students write their own number sentences. Early pages introduce facts through missing-number practice and picture-based sets, then move into three-addend addition and a color-by-code quilt page for subtraction facts. A 'Checking Subtraction' page has students subtract, then write the matching addition equation to verify their answer, and a review page asks them to judge whether a solved equation is correct and fix it if it is not. The workbook closes with five pages of addition and subtraction word problems, ending in a mixed page where students write and solve their own number sentences.