The proposed revisions to the "Australian Curriculum: Mathematics" highlight the importance of learning to mathematise, problem-solve and reason in real world contexts, including financial contexts. Through the Economics + Maths = Financial Capability research project, the authors have been imagining fresh ideas for connecting the "Australian Curriculum's Mathematics and Humanities and Social Sciences" (HaSS) learning areas. In the article, the authors offer a learning sequence where students learn to mathematise, problem-solve and reason in financial contexts. They present two mathematical modelling tasks with a focus on fast fashion, textile waste, and purchasing behaviour--important financial contexts that might be productively explored through mathematical modelling.