Hi Robby. This is a kind of hard problem for 7th grade - good for you for trying to figure it out!

Let's start with some algebra:
Let m = the number of men, w = the number of women and c = the number of children.

Then m + w + c = 100, because there are 100 people in all.

Also, 3m + 2w + (1/2)c = 100, because we want the 100 bushels to divide evenly according to the proportions given.

We can re-write these both. The first one can be written like this:

100 - m - w = c

and the second can be written:

100 - 3m - 2w = (1/2)c.

Double the last line and you get:

200 - 6m - 4w = c.

Notice that we have two equations ending in "= c". Now, remember that two things that both equal a third thing have to equal each other, so that means:

100 - m - w = 200 - 6m - 4w

and this simplifies to

3w = 100 - 5m.

There is a lot of information in this equation. First of all the right side is divisible by 5 so the left side is divisible by 5. Since 3 is not divisible by 5, w must be divisible by 5. Hence the only possibilities for w are 0, 5, 10, ..., 100.

But w certainly can't be 100 since 3 w would be 300. So how large can w be? If w = 35 then 3 w = 105 which is too large so w can only be 0, 5, 10, 15, 20, 25 or 30. That's only 7 cases so you can try them all.

For each possible w find m using 3w = 100 - 5m and then c using m + w + c = 100 and check to see if
3m + 2w + (1/2)c = 100.

Hope this helps,
Stephen and Penny.