764 номер. помогите пожалуйста

Question

764 номер. помогите пожалуйста

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Answer 1

1/3х+1/5х+1/6х=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=3/4
ответ: 3/4
1/4х+1/6х+1/8х=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=9/7=1.2/7
ответ: 1.2/7

Answer 2

764
1)/ (1/3)Х+(1/5)Х+(1/6)Х=21/40
(10Х+12Х+5Х)/30=21/40
(27/30)Х=21/40
Х=(21/40) : (27/30)=(21*30) /(40*27)=7/12

2). (1/4)Х+(1/6)Х+(1/8)Х=39/56
(6Х+4Х+3Х)/24=39/56
(13/24)Х=39/56
Х=39/56 : 13/24=(39*24)/(56*13)=9|7= 1 2|7