Chọn câu đúng

\[\frac{{28}}{{15}}.\frac{1}{{{4^2}}}.3 + \left( {\frac{8}{{15}} - \frac{{69}}{{60}}.\frac{5}{{23}}} \right):\frac{{51}}{{54}}\]

\( = \frac{{28.1.3}}{{{{15.4}^2}}} + \left( {\frac{8}{{15}} - \frac{{23.3}}{{4.3.5}}.\frac{5}{{23}}} \right).\frac{{54}}{{51}}\)

\(\begin{array}{l} = \frac{{7.4.1.3}}{{3.5.4.4}} + \left( {\frac{8}{{15}} - \frac{1}{4}} \right).\frac{{54}}{{51}}\\ = \frac{7}{{20}} + \left( {\frac{{32}}{{60}} - \frac{{15}}{{60}}} \right).\frac{{54}}{{51}}\\ = \frac{7}{{20}} + \frac{{17}}{{60}}.\frac{{54}}{{51}}\\ = \frac{7}{{20}} + \frac{{17}}{{6.10}}.\frac{{6.3.3}}{{17.3}}\\ = \frac{7}{{20}} + \frac{3}{{10}}\\ = \frac{7}{{20}} + \frac{6}{{20}}\\ = \frac{{13}}{{20}}\end{array}\)

Đáp án cần chọn là: D

\[\left( {x + \frac{1}{4} - \frac{1}{3}} \right):\left( {2 + \frac{1}{6} - \frac{1}{4}} \right) = \frac{7}{{46}}\]

\[\left( {x + \frac{1}{4} - \frac{1}{3}} \right):\frac{{23}}{{12}} = \frac{7}{{46}}\]

\[x + \frac{1}{4} - \frac{1}{3} = \frac{7}{{46}}.\frac{{23}}{{12}}\]

\[x + \frac{1}{4} - \frac{1}{3} = \frac{7}{{24}}\]

\[x = \frac{7}{{24}} - \frac{1}{4} + \frac{1}{3}\]

\[x = \frac{3}{8}\]

Đáp án cần chọn là: D