“…Further, they often solve mathematical equivalence problems incorrectly by adding up all of the numbers in the problem or only the numbers before the equal sign (e.g., answering 15 or 12 for 3 + 4 + 5 = 3 + ☐, rather than 9; McNeil & Alibali, 2005). Unfortunately, children's difficulties with mathematical equivalence are often robust, persisting into middle school, high school, and even adulthood (e.g., Chesney & McNeil, 2014;Knuth et al, 2006;McNeil & Alibali, 2005;McNeil, Rittle-Johnson, Hattikudur, & Petersen, 2010). In sum, evidence from past research stresses the importance of establishing understanding of mathematical equivalence early in elementary school.…”