The advent of the digital economy and new technologies requires new human competencies,
including specifically, inter-disciplinary competencies. The current education system is organized
around subjects and more relevant inter-disciplinary training requires new organizational and
methodological foundations. There is a need to develop functional literacy, which implies the ability
of the individual to adapt and continuously develop in a dynamic and complex world, to initiate, and
to implement innovations using knowledge from different industries. The aim of this research was to
develop and implement a system of organizational and methodological tools for inter-disciplinary
learning as a means of developing functional literacy of children and adolescents in general
education organizations within Russia to help them adapt successfully to the digital economy. The
research used analysis of modern theoretical and methodological approaches and practices to the
organization of inter-disciplinary training in educational organizations, from observation, focus
groups and experiments. Part of that functional literacy is the concept of mathematical literacy. In
addition to developing cross-subject tasks, mathematical literacy was analyzed through mathematical
content and mental activity. The article describes the authors' experience in developing cross-subject
tasks to develop research competence, motivation for knowledge and personal development, and
mathematical literacy of students in grades 5-9 (similar to the PISA-2021 research model). It then
describes the methodology and foundations for creating competence-oriented cross-subject tasks
and the development of functional literacy. These are added to specific, proven tools for improving
the effectiveness of inter-disciplinary learning. This creates an environment and conditions for the
development of a person who can think creatively using the competencies of the inter-disciplinary
complex. The article will be of interest to a wide audience of specialists in the field of educational
policy and practice.