B

307-[ ( 180-160) : 2² + 9] : 2

=307-[ 20 : 4 + 9] : 2

=307-[ 5+ 9] : 2

=307-14 : 2

=307-7

=300

205 - [(1200 - (4^2 - 2 . 3)^3 ] : 40

= 205 - [(1200 - (16 - 2 . 3)^3 ] : 40

= 205 - [1200 - (16 - 6)^3 ] : 40

= 205 - [1200 - 10^3 ] : 40

= 205 - [1200 - 1000 ] : 40

= 205 - 200  : 40

= 205 - 5 

= 200

177 : [ 2 . ( 4^2 -9 ) + 3^2 (15 -10)] = 177 : [ 2 . (16 - 9) + 9 . 5 ]

= 177 : [ 2 . 7 + 9 .5 ]

= 177 : [ 14 + 45 ]

= 177 : 59 =3

[(25 - 2^2 . 3) + (3^2 . 4 + 16)] : 5

= [(25 - 4 . 3) + (9 . 4 + 16)] : 5

= [(25 - 12) + (36 + 16)] : 5

= [13 + (36 + 16)] : 5

= [13 + 52] : 5

= 65 : 5

= 13

125(28+72)-25(3^2.4+64)

=125.100-25(9.4+64)

=125.100-25(36+64)

=125.100-25.100

=(125-25).100

=100.100=10000

\(a,A=\dfrac{5-\dfrac{5}{3}+\dfrac{5}{9}-\dfrac{5}{27}}{8-\dfrac{8}{3}+\dfrac{8}{9}-\dfrac{8}{27}}:\dfrac{-15+\dfrac{15}{11}-\dfrac{15}{121}}{16-\dfrac{16}{11}+\dfrac{16}{121}}\)

\(b,B=\dfrac{0,75-0,6+\dfrac{3}{7}+\dfrac{3}{13}}{2,75-2,2+\dfrac{11}{7}+\dfrac{11}{13}}\)

\(a,x+\dfrac{3}{5}=\dfrac{1}{3}\)

\(b,x-\dfrac{2}{5}=\dfrac{-1}{15}\)

\(c,\dfrac{3}{4}-x=\dfrac{2}{7}\)

\(d,-x-\dfrac{3}{7}=\dfrac{1}{21}\)

\(e,-x+\dfrac{4}{3}=\dfrac{1}{2}\)

\(f,\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)