Выполните сложение: 11/20 + 6/15

Выполните вычитание: а) 1/11 - 1/33 в) 13/30 - 2/45 д) 13/60 - 7/40 б) 7/11 - 7/12 г) 7/15 - 2/5 e) 11/21 - 3/14

решите уровнение

x+2/9=5/6

y-3/28=12/35

11/20 + 6/15 = (11•3) / (20•3) + (6•4) / (15•4) = 33/60 + 24/60 = 57/60 = 19/20

{57/60 сократили значит поделили на 3}

а) 1/11 - 1/33 = (1•3) / (11•3) - 1/33 = 3/33 - 1/33 = 2/33

в) 13/30 - 2/45 = (13•3) / (30•3) - (2•2) / (45•2) = 39/90 - 4/90 = 35/90 = 7/18

{35/90 сократили на 5}

Д) 13/60 - 7/40 = (13•2) / (60•2) - (7•3) / (40•3) = 26/120 - 21/120 = 5/120 = 1/24

{5/120 сократили на 5}

б) 7/11 - 7/12 = (7•12) / (11•12) - (7•11) / (12•11) = 84/132 - 77/132 = 7/132

Г) 7/15 - 2/5 = 7/15 - (2•3) / (5•3) = 7/15 - 6/15 = 1/15

Е) 11/21 - 3/14 = (11•2) / (21•2) - (3•3) / (14•3) = 22/42 - 9/42 = 13/42

Х+2/9=5/6

Х=5/6 - 2/9

Х = (5•3) / (6•3) - (2•2) / (9•2)

Х = 15/18 - 4/18

Х = 11/18

Проверка

11/18+2/9=11/18 + (2•2) / (9•2) = 11/18 + 4/18 = 15/18 = 5/6

У - 3/28 = 12/35

У = 12/35 + 3/28

У = (12•4) / (35•4) + (3•5) / (28•5)

У = 48/140 + 15/140

У = 63/140 = 9/20

{63/140 сократили на 7}

Проверка

9/20 - 3/28 = (9•7) / (20•7) - (3•5) / (28•5) = 63/140 - 15/140 = 48/140 = 12/35