Formulate and solve problems using equations and inequalities from linear, quadratic, simple rational, and exponential functions. Develop equations incorporating two or more variables to show relationships between quantities and represent them graphically with appropriately labeled and scaled axes. Use equations, inequalities and systems of these as constraints, interpreting solutions in a real-world context, such as optimizing food combinations based on nutritional and cost restrictions. Alter formulas to emphasize a specific variable, following the same logic used in equation solving like reorganizing Ohm's law V= IR to focus on resistance R.