This book summarises various reactions to school closure due to COVID-19, particularly focusing on the digitalization of education, government, schools, and the private sector. The authors aim to demonstrate connections that exist between the notion of technology immune-technology enabled mathematics problem-solving pedagogy and the theory of instrumental genesis. This theory has been used by educational researchers to demonstrate the modern-day pedagogical appropriation of an artifact as a material object. The development, implementation and evaluation of a mixed-mode delivery method involving a well-designed user interface and mobile learning applications is discussed. The concluding study presents some implementations of Newton-Cotes integration methods to nonlinear 2D integrals with a new calculator: TWOD_integral_calculator designed with the help of Matlab Graphical User Interface.