Tính: a) (-0,5) - (-1 + 2/3) : 1,5 + (-1/4); b) [(-7/8) : 21/16] - 5/3.(1/3-7/10)

* Hướng dẫn giải

a) $(-0,5)-(-1+\frac{2}{3}):1,5+\left(\frac{-1}{4}\right)$

$=\left(\frac{-1}{2}\right)-(\frac{-3}{3}+\frac{2}{3}):\frac{3}{2}+\left(\frac{-1}{4}\right)$

$=\left(\frac{-1}{2}\right)-\left(\frac{-1}{3}\right).\frac{2}{3}+\left(\frac{-1}{4}\right)$

$=\left(\frac{-1}{2}\right)+\frac{2}{9}+\left(\frac{-1}{4}\right)$

$=\left(\frac{-18}{36}\right)+\frac{8}{36}+\left(\frac{-9}{36}\right)=\frac{-19}{36}$