Cho biểu thức: A = (2 + 1/3 - 2/5) - (7 - 3/5 - 4/3) - (1/5 + 5/3 - 4)

a) Tính giá trị từng biểu thức trong dấu ngoặc trước

A = $\left(2+\frac{1}{3}-\frac{2}{5}\right)-\left(7-\frac{3}{5}-\frac{4}{3}\right)-\left(\frac{1}{5}+\frac{5}{3}-4\right)$

$A=\left(\frac{30}{15}+\frac{5}{15}-\frac{6}{15}\right)-\left(\frac{105}{15}-\frac{9}{15}-\frac{20}{15}\right)-\left(\frac{3}{15}+\frac{25}{15}-\frac{60}{15}\right)$

$A=\left(\frac{30+5-6}{15}\right)-\left(\frac{105-9-20}{15}\right)-\left(\frac{3+25-60}{15}\right)$

$A=\frac{29}{15}-\frac{76}{15}-\frac{-32}{15}$

$A=\frac{29-76+32}{15}=\frac{-15}{15}=-1$

b) $A =\left(2+\frac{1}{3}-\frac{2}{5}\right)-\left(7-\frac{3}{5}-\frac{4}{3}\right)-\left(\frac{1}{5}+\frac{5}{3}-4\right)$

$A=2+\frac{1}{3}-\frac{2}{5}-7+\frac{3}{5}+\frac{4}{3}-\frac{1}{5}-\frac{5}{3}+4$

$A=\left(\frac{1}{3}+\frac{4}{3}-\frac{5}{3}\right)+\left(\frac{3}{5}-\frac{2}{5}-\frac{1}{5}\right)+\left(2-7+4\right)$

$A=\frac{0}{3}+\frac{0}{5}+(-1)$

A = -1