Assuming that the number of chickens bought by roosters, hens and chickens is X Y Z, two equations 5x+3y+(1/3) z =100x+y+z =100 are obtained.

X stands for y and z respectively, and the expression of Y Z is Y=25-(7/4)x Z=75+(3/4)x because I want to buy an integer number of chickens (hide the topic, don't ask me why). . All right. For the life of the penis. You can only buy an integer number of chickens, so there is a multiple of x to 4. Y cannot be negative.

So I got four sets of answers. When x = 0y = 25z = 75x = 4y =18z = 78x = 8y =1z = 81x =12y = 4z = 84.