Final answer:
An inequality example is x > 3, representing numbers greater than 3. A real-life example is a movie theater where children ages 12 and up pay for tickets, expressed as c ≥ 12. The concept of subtraction is evident in economic models, such as the demand equation for pizzas.
Step-by-step explanation:
Writing and Solving an Inequality
To write an inequality that requires using addition or subtraction to solve, we can use an example where the graph shows a solution for x greater than a certain value. For instance, if the graph indicates that the solution for x is all values greater than 3, the inequality can be written as x > 3. To solve this inequality, we would simply state that x can be any number larger than 3.
Real-life situation: A movie theater allows free entry for children under 12 years of age. If c represents the age of a child, then the inequality describing paying customers is c ≥ 12. This means that any child who is 12 years old or older will have to pay for a ticket.
To connect our knowledge to the provided information about the demand equation for personal pizzas, Qd = 16 - 2P, it is clear that as the price (P) of pizzas increases, the quantity demanded (Qd) decreases. This demonstrates an understanding of subtraction in the context of a real-life economic model, where the price of an item affects the demand.