(1/4+1/5)*х=1 целая 4/5
(1/4 + 1/5) * x = 1 4/5 (5/20 + 4/20) * x = 1 4/5 9/20x = 9/5 x = 9/5 : 9/20 x = 9/5 * 20/9 x = 4 ----------
спасибо