Đề bài 

= ( 5/12 +    1/6 ) : (    2/3 - 1/12 ) 

= ( 5/12 + 2/12 ) :   ( 8/12 - 1/12 ) 

= 7/12 : 7/12 

= 1 

K Trắng nha .

=1 nha

\(\left(\frac{5}{12}+\frac{1}{2}\times\frac{1}{3}\right):\left(2\times\frac{1}{3}-1\times\frac{1}{12}\right)\)

\(=\left(\frac{5}{12}+\frac{1}{6}\right):\left(\frac{2}{3}-\frac{1}{12}\right)\)

\(=\frac{7}{12}:\frac{7}{12}\)

\(=1\)

k bk tính nhanh!

1234567890

5/2\(\times\)1=\(\frac{5}{2\times1}hay=\frac{5}{2}\times1\)

\(A=\frac{5}{2\times1}+\frac{4}{1\times11}+\frac{3}{11\times2}+\frac{1}{2\times15}+\frac{13}{15\times4}\)

      \(=\frac{5}{2}+\frac{4}{11}+\frac{3}{22}+\frac{1}{30}+\frac{13}{60}\)

        \(=\frac{13}{4}\)hoặc 3,25

Vậy A = 13/4 hoặc 3,25

1+2x1+3=1+(2x1)+3=1+2+3=3+3=6

1/2x1/3+1/3-1/4+1/4x1/5

= 1/2-1/3+1/3-1/4+1/4-1/5

=1/2-1/5

=3/10. (1/2x1/3= 1/2x3) 

1/2x1/3+1/3-1/4+1/4x1/5 = 1/2-1/3+1/3-1/4+1/4-1/5 =1/2-1/5 =3/10. (1/2x1/3= 1/2x3)