Let C be the number of cows and H be the number of horses. From the condition, you have this system of 2 equations in 2 unknowns C = 3H, (1) C + H = 112. (2) Solve it by the substitution method. From equation (1), you just have an expression for C. Substitute it into equation (2), replacing C: 3H + H = 112, 4H = 112 H = 112/4 = 28. Answer. 28 horses and 3*28 = 84 cows.