trả lời 

đúng 

vì x là 1

chúc bn học tốt

\(2\frac{3}{4}< 2.\frac{3}{4}\left(s\right)\)

\(2\frac{3}{4}=2\cdot\frac{3}{4}\left(s\right)\)

\(2\frac{3}{4}>2.\frac{3}{4}\left(\text{đ}\right)\)

= 2/21

=9/5

=37/6:\(6\frac{1}{6}\)

=79/20: tự đổi nhe bạn

=3/5__________-

\(\frac{4}{15}x\frac{5}{14}=\frac{4x5}{15x14}=\frac{2x1}{3x7}=\frac{2}{21}\)

\(\frac{3}{4}:\frac{5}{12}=\frac{3}{4}x\frac{12}{5}=\frac{3x12}{4x5}=\frac{3x3}{1x5}=\frac{9}{5}=1,8\)

\(\frac{7}{2}+\frac{8}{3}=\frac{7x3}{2x3}+\frac{8x2}{3x2}=\frac{21}{6}+\frac{16}{6}=\frac{21+16}{6}=\frac{37}{6}\)

a, 3/4 + 1/4.x=2

    1/4.x        = 2-3/4

     1/4.x      =5/4

     x           = 5/4:1/4

     x           = 5

b, x-2/3.9/4=2,5-1/2

    x-2/3.9/4=2

    x-2/3     =2:9/4

    x-2/3   =8/9

     x        = 8/9+2/3

     x         = 14/9

  \(a.\) \(3\frac{3}{4}+\left(4\frac{2}{4}-3\frac{1}{2}\right):\frac{3}{4}\)

\(=\frac{15}{4}\left(\frac{18}{4}-\frac{7}{2}\right):\frac{3}{4}\)

\(=\frac{15}{4}+\frac{4}{4}:\frac{3}{4}=\frac{15}{4}+\frac{4}{3}\)

\(=\frac{15}{4}+\frac{4}{3}=\frac{61}{12}\)

\(b.\) \(7\cdot\frac{2}{3}-\frac{2}{5}:\frac{1}{2}-\frac{2}{3}\)

\(=\frac{7}{3}-\frac{2}{5}\cdot2-\frac{2}{3}\)

\(=\frac{7}{3}-\frac{4}{5}-\frac{2}{3}=\frac{35-12-10}{15}\)

\(=\frac{13}{15}\)

\(c.\) \(68,7-100:20+70,8\)

\(=68,7-5+70,8\)

\(=63,7+70,8\)

\(=134,5\)

\(d.\)\(\left(5915+445:5\right)-76\cdot25\)

\(=\left(5915+89\right)-1900\)

\(=6004-1900=4104\)

a)=\(\frac{15}{4}+\left(\frac{18}{4}-\frac{7}{2}\right)\)/ \(\frac{3}{4}\)

=\(\left(\frac{33}{4}-\frac{14}{4}\right)\)/ \(\frac{3}{4}\)

= \(\frac{19}{4}\cdot\frac{4}{3}\)

=\(\frac{19}{3}\)

b) = \(\frac{2}{3}\cdot\left(7-1\right)-\frac{2}{5}\cdot\frac{2}{1}\)

= \(\frac{2}{3}\cdot6-\frac{4}{5}\)

= 1-\(\frac{4}{5}\)

= \(\frac{1}{5}\)

c) = 68.7 - 5 + 70.8 

= 63.7 + 70.8

=134.5

d) = (5915 - 89) -76*25

= 5826 - 1900

= 3926

\(3\frac{3}{4}\times4=\frac{3\times4+3}{4}\times4=\frac{15}{4}\times4=\frac{15\times4}{4}=15\)

\(4\frac{3}{2}\div1\frac{1}{2}=\frac{4\times2+3}{2}\div\frac{1\times2+1}{2}=\frac{11}{2}\div\frac{3}{2}=\frac{11}{2}\times\frac{2}{3}=\frac{11}{3}\)

\(4\frac{3}{4}+2\frac{3}{2}=\frac{4\times4+3}{4}+\frac{2\times2+3}{2}=\frac{19}{4}+\frac{7}{2}=\frac{19}{4}+\frac{14}{4}=\frac{33}{4}\)

\(3\frac{8}{6}-4\frac{1}{3}=\frac{3\times8+6}{6}-\frac{4\times3+1}{3}=\frac{30}{6}-\frac{13}{3}=\frac{30}{6}-\frac{26}{6}=\frac{4}{6}=\frac{2}{3}\)

\(3\frac{2}{4}\)x 4 = \(\frac{14}{4}\)x 4 = \(\frac{56}{4}\)

\(4\frac{3}{2}\): \(1\frac{1}{2}\)= \(\frac{11}{2}\): \(\frac{3}{2}\)= \(\frac{11}{2}\)x \(\frac{2}{3}\)= \(\frac{22}{6}\)= \(\frac{11}{3}\)

\(4\frac{3}{4}\)+ \(2\frac{3}{2}\)= \(\frac{11}{4}\)+ \(\frac{7}{2}\)= \(\frac{25}{4}\)= 6,25

\(3\frac{8}{6}\)- \(4\frac{1}{3}\)= \(\frac{13}{3}\)- \(\frac{13}{3}\)= 0

\(\frac{2}{3}.\frac{4}{5}+\frac{1}{3}.\frac{4}{5}=\frac{4}{5}\left(\frac{2}{3}+\frac{1}{3}\right)=\frac{4}{5}.\frac{3}{3}=\frac{4}{5}.1=\frac{4}{5}\)

\(\frac{1}{2}:\frac{3}{4}+\frac{1}{6}:\frac{3}{4}=\frac{3}{4}:\left(\frac{1}{2}+\frac{1}{6}\right)=\frac{3}{4}:\frac{2}{3}=\frac{9}{8}\)

\(\frac{2}{3}.\frac{4}{5}-\frac{1}{3}.\frac{4}{5}=\frac{4}{5}\left(\frac{2}{3}-\frac{1}{3}\right)=\frac{4}{5}.\frac{1}{3}=\frac{4}{15}\)

\(\frac{1}{2}:\frac{3}{4}-\frac{1}{6}:\frac{3}{4}=\frac{3}{4}:\left(\frac{1}{2}-\frac{1}{6}\right)=\frac{3}{4}:\frac{1}{3}=\frac{9}{4}\)

\(\frac{2}{3}.\frac{4}{5}+\frac{1}{3}.\frac{4}{5}=\left(\frac{2}{3}+\frac{1}{3}\right).\frac{4}{5}=1.\frac{4}{5}=\frac{4}{5}\)

\(\frac{1}{2}:\frac{3}{4}+\frac{1}{6}:\frac{3}{4}=\frac{1}{2}.\frac{4}{3}+\frac{1}{6}.\frac{4}{3}=\left(\frac{1}{2}+\frac{1}{6}\right).\frac{4}{3}=\frac{2}{3}.\frac{4}{3}=\frac{8}{9}\)

c,d tương tự 

1/2

7/3

1/4

11/4

19/5

\(\frac{1}{2}=0,5\)

\(2\frac{1}{3}=\frac{7}{3}\)

\(\frac{1}{4}=0,25\)

\(2\frac{3}{4}=\frac{11}{4}=2,75\)

\(3\frac{4}{5}=\frac{19}{5}=3,8\)

ai giải được

\(8\frac{7}{10}+2\frac{3}{4}=\frac{87}{10}+\frac{11}{4}=\frac{174}{20}+\frac{55}{20}=\frac{229}{20}\)

Bạn chỉ cần đưa về phân số xong tính bình thường. Muốn đổi từ hỗn số sang phân số, ta chỉ cần lấy phần nguyên nhân cho mẫu rồi cộng với tử là xong. Chứ bạn cứ hỏi mấy bài dễ như thế này thì k giỏi đc đâu!!!