\input zb-basic \input zb-matheduc \iteman{ZMATH 2016d.00742} \itemau{Wells, Pamela J.} \itemti{Understanding linear functions and their representations.} \itemso{Math. Teach. Middle Sch. 21, No. 5, 308-313 (2015).} \itemab Summary: Linear functions are an important part of the middle school mathematics curriculum. Students in the middle grades gain fluency by working with linear functions in a variety of representations. Presented in this article is an activity that was used with five eighth-grade classes at three different schools. The activity contains 15 cards that can be sorted to create 4 sets of cards, with each set representing one particular linear function. Some cards will not fit into any set, which automatically increases the cognitive demand of the task. (ERIC) \itemrv{~} \itemcc{I23} \itemut{linear functions; graph of a function; rate of change; vertical intercept} \itemli{http://www.nctm.org/Publications/Mathematics-Teaching-in-Middle-School/2015/Vol21/Issue5/Understanding-Linear-Functions-and-their-Representations/} \end