Why are math modeling problems the source of such frustration for students and teachers? The conceptual understanding that students have when engaging with a math modeling problem varies greatly. They need opportunities to make their own assumptions and design the mathematics to fit these assumptions (CCSSI 2010). Making these assumptions is part of an interpretative process (NCTM 2000) that depends on students' prior experiences. Furthermore, students have different life and classroom experiences that can lead to distinct (but acceptable) mathematical models. This article will illustrate some challenges to teaching mathematical modeling in the classroom: (1) how to engage students in mathematical modeling; (2) respond to different answers; and (3) take into account that students draw on their realistic experiences. When students produce answers that originate from their unique perspectives, those answers might seem wrong at first but may be valid.