Решите уровнение и сделай-те проверку 1)1/4х+1/х=5/16 2)1/х-1/9х=2/9 3)1/8х+1/х=3/8 4)1/х-1/5х=2/15 / это дробная черта)

1) 1/3х + 1/5х + 1/6х = 21/40 1*10/3*10х + 1*6/5*6х + 1*5/6*5х = 21/40 10/30х + 6/30х + 5/30х = 21/40 21/30х = 21/40 х = 21/40 : 21/30 х = 21/40 * 30/21 х = 21*30/40*21 х = 30/40 х = 3/4 проверка: 1/3 * 3/4 + 1/5 * 3/4 + 1/6 * 3/4 = 21/40 3/12 + 3/20 + 3/24 = 21/40 3*10/12*10 + 3*6/20*6 + 3*5/24*5 = 21/40 30/120 + 18/120 + 15/120 = 21/40 63/120 = 21/40 21/40 = 21/40 2) 1/4х + 1/6х + 1/8х = 39/56 1*6/4*6х + 1*4/6*4х + 1*3/8*3х = 39/56 6/24х + 4/24х + 3/24х = 39/56 13/24х = 39/56 х = 39/56 : 13/24 х = 39/56 * 24/13 х = 39*24/56*13 х = 3*24/56 х = 72/56 х = 72: 2/56: 2 х = 36/28 х = 36: 4/28: 4 х = 9/7 или 1 2/7 проверка: 1/4 * 9/7 + 1/6 * 9/7 + 1/8 * 9/7 = 39/56 9/28 + 9/42 + 9/56 = 39/56 9*6/28*6 + 9*4/42*4 + 9*3/56*3 = 39/56 54/168 + 36/168 + 27/168 = 39/56 117/168 = 39/56 39/56 = 39/56

Подешевел на 20 %

Т. е. на этой неделе скейт стоит на 20 % меньше от цены на недели

20 % = 0,2

65*0,2=13

ответ: 13 евро