Thực hiện phép tính, tính nhanh (nếu có thể): (a) ( 3/5 − 8/15 ) : 2/3 . (b) 23/18 + − 41/15 − 23/18 + 11/15 + 8/5 .

a) \(\left( {\frac{3}{5} - \frac{8}{{15}}} \right):\frac{2}{3}\)

\( = \left( {\frac{9}{{15}} - \frac{8}{{15}}} \right).\frac{3}{2}\)

\( = \frac{1}{{15}}.\frac{3}{2} = \frac{1}{{10}}\).

b) \(\frac{{23}}{{18}} + \frac{{ - 41}}{{15}} - \frac{{23}}{{18}} + \frac{{11}}{{15}} + \frac{8}{5}\)

\( = \left( {\frac{{23}}{{18}} - \frac{{23}}{{18}}} \right) + \left( {\frac{{ - 41}}{{15}} + \frac{{11}}{{15}}} \right) + \frac{8}{5}\)

\( = 0 - 2 + \frac{8}{5} = \frac{{ - 2}}{5}\).

c) \(4\frac{1}{3}.\frac{{15}}{{29}} + 4\frac{1}{3}.\frac{{14}}{{29}} - \frac{1}{3}\)

\( = \frac{{13}}{3}.\left( {\frac{{15}}{{29}} + \frac{{14}}{{29}}} \right) - \frac{1}{3}\)

\( = \frac{{13}}{3}.1 - \frac{1}{3}\)

\( = \frac{{13}}{3} - \frac{1}{3} = \frac{{12}}{3} = 4\).