Tìm x, biết a) x - 5/12 - 4/9 = -13/18 b) 2 - (x + 3/7) = 9/-21

* Hướng dẫn giải

a)

$\begin{array}{l}x-\frac{5}{12}-\frac{4}{9}=\frac{-13}{18}\\ x=\frac{-13}{18}+\frac{5}{12}+\frac{4}{9}\\ x=\frac{-26}{36}+\frac{15}{36}+\frac{16}{36}\\ x=\frac{5}{36}\end{array}$

b)

$\begin{array}{l}2-\left(x+\frac{3}{7}\right)=\frac{9}{-21}\\ 2-x-\frac{3}{7}=\frac{-3}{7}\\ -x=\frac{-3}{7}+\frac{3}{7}-2\\ -x=-2\\ \Rightarrow x=2\end{array}$