Tính a) -2,4 + 1 1/2 : (1 - 2/3) b) 1/7 . 3 9/10 - 1/7 . 9/10

* Hướng dẫn giải

a) $-2,4+1\frac{1}{2}:\left(1-\frac{2}{3}\right)=-\frac{12}{5}+\frac{3}{2}.3=-\frac{12}{5}+\frac{9}{2}=\frac{21}{10}.$

b) $\frac{1}{7}.3\frac{9}{10}-\frac{1}{7}.\frac{9}{10}=\frac{1}{7}.\left(3\frac{9}{10}-\frac{9}{10}\right)=\frac{3}{7}.$