ọi tuổi cha là a=> tuổi con gái là 2/5 a=> tuổi con trai là 3/4*2/5a=3/10a
ta có a+2/5a+3/10a = 85
=> 17 /10a= 85
=> a= 50
=> bố 50 tuổi, con gái: 2/5*50= 20 tuổi, con trai: 85-50-20=15 tuổi

k cho mink nhe

AI TRA LOI TRUOC MINH SE cho 1 dung nho co loi giai ,dap so .ko tra loi linh tinh cam on nhieu cac ban giup minh nhe

Hi everybody . My name is Nhu Y, I am 11 years old and I am a student of grade 6B junior high school in Hai Lam. My favorite subject is English. My favorite sport is badminton, .... I usually watch TV in my free time. I go to school from Monday to Saturday. I always do my homework every morning. I love my family . My family has 7 people: three, me, 3 brothers, 1 head and me. My husband is a farmer, my mother too.My first brother is an electrician, his second brother is a mechanic, his third brother is a bricklayer. My sister is a worker. and i am a student, ...

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# MissyGirl #

Dịch là:

Hi everybody . My name is Nhu Y, I am 11 years old and I am a student in grade 6B Hai Lam secondary school. My favorite subject is English. My favorite sport is badminton, .... I usually watch TV in my free time. I go to school Monday through Saturday. I always do my homework every morning. I love my family. My family has 7 people: three, mother, 3 brother, 1 sister and me. My father is a farmer, so is my mother. My first brother is an electrician, his second brother is a chameleon, his third brother is a nephew. My sister is a worker. And I'm a student, ...

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Gọi số học sinh giỏi là a, số học sinh khá là b, học sinh cả lớp là c

Ta có: a=1/5.c+3

           b=1/2.c+9

           a+b=c

=>1/5.c+3+1/2.c+9=c

=>7/10.c+12=c

=>c-7/10.c=12

=>3/10.c=12

=>c=12:3/10

=>c=40

Vậy lớp 5b có 40 học sinh

 Số học sinh trung bình chiếm :

  1 - 3/8 - 1/2 = 1/8 ( số học sinh )

Số học sinh của lớp đó :

  4 : 1/8 = 32 ( học sinh )

   đ/s : ...