Despite its apparent simplicity, the reversal error, consisting in reversing the relationship between two variables in a mathematical word problem, has always been an issue in mathematics education. In this paper, we present POETIC, an interactive web-based environment developed to teach users to avoid this error. The effectiveness of this web-based environment is tested via the Test-Case and the Room-Metaphor approaches, two types of novel interactive visualization used by POETIC. A crowdsourcing-based comparison study with 200 participants showed that both approaches decreased the frequency of reversal errors in certain types of word problems. The main conclusion of our study is that interactive visualization of equations can be a tool to reduce this type of error.