Republican, I tried more than an hour finding it mathematically, but everytime I get dog = $0. This is what I did. Please tell me where I am wrong, if I am. 1 cow's price = $x i.e. c = x Total number of cows = n Also, x = n Total cow's price = c * n = x * x = x^2 For goat, 1 goat = $10 In terms of price, x^2 = 10g + chicken -------- (i) According to given condition: (Understand the equation in terms of price) (X^2)/2 = [ (10g - g) / 2 ] + chicken + dog (X^2)/2 = (10g - 10) / 2 + c + d ------- (ii) From equation (i) and (ii), 10g + c = 5g - 5 + c + d; Therefore, 10g + c = 5g - 5 + 10 (given, g = c + d = 10) (10g + c) / 2 = 5g + 5 10g + c = 10g + 10 Therefore, c = 10; Hence, dog's price = $0 Well, it works mathematically that chicken also cost $10...maybe the those two guys just bought the chicken to make us confuse! Please tell me where I am wrong on the above solution!