Final answer:
To find out how many people attended the reunion last year when the attendance this year is given as 160 people, we can set up an equation using the given information and solve for the unknown variable.
Step-by-step explanation:
To find out how many people attended the reunion last year, we can set up an equation using the given information. Let's assume the attendance last year was 'x'. We are told that this year's attendance is 25% of last year's attendance, so we can write the equation as: 0.25x = 160. To solve for 'x', we divide both sides of the equation by 0.25: x = 160 ÷ 0.25 = 640. Therefore, 640 people attended the reunion last year.