a) =\(\dfrac{21}{35}+\dfrac{10}{35}+\dfrac{4}{35}=\dfrac{21+10+4}{35}=\dfrac{35}{35}=1\)
b) =\(\dfrac{16}{24}+\dfrac{15}{24}-\dfrac{12}{24}=\dfrac{19}{24}\)
c) =\(\dfrac{35}{40}+\dfrac{80}{40}-\dfrac{24}{40}+\dfrac{120}{40}=\dfrac{35+80-24+120}{40}=\dfrac{211}{40}\)

ai giải hộ mik điiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii mà

Bài 1: 

a: =2/3+7/5=10/15+21/15=31/15

b: =3/4+1/8=6/8+1/8=7/8

c: =225/25+7/25=232/25

d: =5/8+8=64/8+5/8=69/8

a) \(x+\dfrac{4}{5}=\dfrac{45}{5}-\left(\dfrac{3}{7}+\dfrac{3}{5}\right)\)

   \(x+\dfrac{4}{5}=\dfrac{45}{5}-\dfrac{36}{35}\)

  \(x+\dfrac{4}{5}=\dfrac{279}{35}\)

  \(x=\dfrac{279}{35}-\dfrac{4}{5}\)

  \(x=\dfrac{251}{35}\)

b) \(\dfrac{5}{8}\times x=\dfrac{4}{5}\)

            \(x=\dfrac{4}{5}\div\dfrac{5}{8}\)

            \(x=\dfrac{32}{25}\)

a) x + 4/5 = 45/5 - (3/7 + 3/5)
    x + 4/5 = 45/5 - 36/35

    x + 4/5 = 279/35

           x   = 279/35 - 4/5

           x   = 251/35

vậy x =...

b) 5/8 x X = 4/5 

             X = 5/8 : 4/5

             X = 32/25

vậy x =...

ĐỌC TIẾP Ý

Câu 1: D

Câu 2: Các phân số tối giản là \(\dfrac{1}{9};\dfrac{2}{11}\)

Câu 3: Phân số lớn nhất là \(\dfrac{17}{3}\)

Câu 4:

\(76m^28cm^2=760008cm^2\)

Câu 5:

Gọi số cần tìm là x

Theo đề, ta có: \(\dfrac{4}{7}=\dfrac{x}{21}\)

=>\(x=4\cdot\dfrac{21}{7}=4\cdot3=12\)

a) 

5/6+3/6= 8/6 = 4/3

b)

6/36= 1/6

a) 4/3

b) 1/6

c) 37/15

d) 3

1.B

2.C

3. Thiếu

ĐÂY LÀ CÂU B , C D CỦA CÂU 3 

1.B

2.C

3.B

a: =20/60+12/60-15/60=17/60

b: =7/8-1/4-2/5=7/8-2/8-2/5=5/8-2/5=25/40-16/40=9/40

c: =5/11-3/5+6/11=1-3/5=2/5