Let x = the number of C. Then the number of A is x+26 and the number of B is x+12, according to the condition. You have then this equation for the total x + (x+26) + (x+12) = 581 which gives 3x = 581 - 26 - 12 = 543, x = 543/3 = 181. ANSWER. C = 181; A = 181 + 26 = 207 and B = 181 + 12 = 193.