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