Question

[Linh Luna]

Tìm x biet

A, 2/3 × x - 4/7 = 1/8

B, 2/7 - 8/9 × x = 2/3

C, 4/7 + 5/9 : x = 1/5

Answer 1

[Nguyễn Đắc Định]

a)

\(\dfrac{2}{3}\cdot x-\dfrac{4}{7}=\dfrac{1}{8}\\ \dfrac{2}{3}\cdot x=\dfrac{1}{8}+\dfrac{4}{7}\\ \dfrac{2}{3}\cdot x=\dfrac{39}{56}\\ x=\dfrac{39}{56}:\dfrac{2}{3}\\ x=\dfrac{117}{112}\)

b)

\(\dfrac{2}{7}-\dfrac{8}{9}\cdot x=\dfrac{2}{3}\\ \dfrac{8}{9}\cdot x=\dfrac{2}{7}-\dfrac{2}{3}\\ \dfrac{8}{9}\cdot x=-\dfrac{8}{21}\\ x=-\dfrac{8}{21}:\dfrac{8}{9}\\ x=-\dfrac{3}{7}\)

c)

\(\dfrac{4}{7}+\dfrac{5}{9}:x=\dfrac{1}{5}\\ \dfrac{5}{9}:x=\dfrac{1}{5}-\dfrac{4}{7}\\ \dfrac{5}{9}:x=-\dfrac{13}{35}\\ x=\dfrac{5}{9}:\left(-\dfrac{13}{35}\right)\\ x=-\dfrac{175}{117}\)

Answer 2

[Phương Thảo]

Lấy máy tính ra ấn là đc mà bạn