The paper describes strategies for remediating mathematics difficulties (particularly the process of regrouping or "borrowing" in whole number subtraction) in children. Three interrelated aspects of the process (the meaning of subtraction, understanding of non-standard numerals, and the function of the subtraction algorithm), are considered. The set-subset model for learning subtraction, in which children manipulate concrete objects in an illustration of the part-whole inclusion relationship, is described. The difficulties facing children with reversal problems in dealing with value concepts are noted. The part-total terms is illustrated as one way of teaching the subtraction algorithm, while the comparison model is viewed as an alternative approach. The author suggests that parents and teachers should be wary of computer materials designed for learning disabled children. (CL)