After graduating from the University of Guelph, Rex conducted research in horticulture, with a focus on forest seedling production and medicinal plants. He designed experiments to improve plant growth and production, collected and analysed data, and wrote research reports. After 10 years, he changed profession to become a teacher. He has been teaching mathematics for more than 20 years, having taught at Collingwood School, Kwantlen Polytechnical University, and Crofton House School. Along the way, he was also doing financial calculations as a mortgage broker. Having applied mathematics in the real world, he incorporates his science and financial experiences into his classes.