Thực hiện phép tính (hợp lí nếu có thể): - 0,25 + 2/3

a) \( - 0,25 + \frac{2}{3}\)

 \[ = \frac{{ - 1}}{4} + \frac{2}{3}\]

 \[ = \frac{{ - 3}}{{12}} + \frac{8}{{12}} = \frac{5}{{12}}\]

 b) \(1\frac{4}{{23}} + \frac{{ - 5}}{{21}} - \frac{4}{{23}} + 0,5 - \frac{{16}}{{21}}\)

 \[ = \left( {1\frac{4}{{23}} - \frac{4}{{23}}} \right) + \left( {\frac{{ - 5}}{{21}} - \frac{{16}}{{21}}} \right) + 0,5\]

 \[ = 1 + \left( { - 1} \right) + 0,5 = 0,5\]

 c) \(2 - \left[ {{{\left( {1 - \frac{1}{3}} \right)}^{12}}:{{\left( {\frac{2}{3}} \right)}^{10}} - 1\frac{4}{9} - {{2023}^0}} \right]\)

 \[ = 2 - \left[ {{{\left( {\frac{2}{3}} \right)}^2} - \frac{{13}}{9} - 1} \right]\]

 \[ = 2 - \left[ {\frac{4}{9} - \frac{{13}}{9} - 1} \right] = 2 - \left( { - 2} \right) = 4\]