Before sale: 7x/25 sheep and 18x/25 goat.
After sale: 63x/ 125 sheep, 62x/ 125 goat;
Get the equation:
7x/25-a+84 = 63x/ 125-( 1)
18x/25-(84-a)= 62x/ 125-(2)
(1)(2) The same equation is obtained after sorting.
x = 125* (84-a)/28
= 125*(3 - a/28)
Obviously, to make X a positive integer, A must be a multiple of 28, and 0 ≤ a/28 ≤2.
When a/28=0, that is, a=0, x=375:
Pre-sale: sheep =105; Goat = 270;
After sale: sheep =189; Goat =186;
The number of sheep is less than the original goat: 270- 189=8 1 (only)
When a/28= 1, that is, a=28 and x=250:
Before buying and selling: sheep = 70; Goat =180;
After sale: sheep =126; Goat =124;
The number of sheep is less than the original goat: 180- 126=54 (only)
When a/28=2, namely a=56, x= 125:
Before buying and selling: sheep = 35
Conclusion: The number of sheep is 8 1, that is, 54, which is less than the original goat.