Answer:
40 people are currently planning to attend the reunion.
Explanation:
If we don't know how many people are coming, we can call that number x.
If those people split the cost ($200) it will be 200/x.
If 10 more people come, the head count is now x+10.
So the cost becomes 200/(x+10)
The cost when more people pitch in is less money per person. If fewer people split the cost its more per person. They are saying the difference here is $1.
So we can write an equation.
200/x = 200/(x+10) + 1
OR
200/x - 1 = 200/(x+10)
Cross multiply. This gives you a quadratic equation so factor to solve or use Quadratic Formula. See image. It shows how to solve by factoring.
see images. There are 2 images.