Final answer:
The student's question involves solving a quadratic equation, understanding regression analysis, and manipulating algebraic expressions to calculate variables like national income.
Step-by-step explanation:
The question seems to be about using mathematical equations to solve for a variable, specifically a quadratic equation. The discussion indicates substituting values into an equation to find y, and it mentions the use of a regression line equation (y = mx + b) in a graph. It also involves calculating national income by replacing T with a percentage of Y to simplify an algebraic expression.
These examples highlight different concepts in algebra and statistics including solving quadratic equations, regression analysis, and algebraic manipulation. By applying these mathematical procedures, you can solve for unknown variables and model relationships between different quantities.