Final answer:
The correct option is a), which states that Lisa is twice as old as she was 15 years ago. The equation x + 15 = 2x perfectly models this situation, making it the problem the equation can solve.
Step-by-step explanation:
The equation x + 15 = 2x can be used to solve a problem that involves a current age and a comparison to an age in the past or future. Let's analyze each option given:
- a) This option suggests that Lisa's current age is twice what it was 15 years ago. This fits the form of the equation where 'x' can represent Lisa's age 15 years ago, and '2x' would be her current age.
- b) In this scenario, the equation doesn't fit because it suggests that Rosa's age in 15 years will be twice what it is now, not that it is twice what it was 15 years ago.
- c) This option is incorrect because it suggests Alexa will be half her current age in 15 years, which is not represented by the equation provided.
- d) This option is incorrect because it suggests that Fiona is currently 15 years old or that when she becomes 15, she'll be twice her current age. This does not correlate with the equation which involves a past age being doubled to equal the present age.
Therefore, the correct problem that can be solved with the equation is option a): Lisa is twice as old as she was 15 years ago. How old is Lisa now?