a. x + 3/10= 25/8
x = 25/8-3/10
x = 113/40
b. x/35 = 4/5-5/7
x/35 = 3/35
vậy x=3
\(x+\dfrac{3}{10}=4-\dfrac{7}{8}\)
\(x+\dfrac{3}{10}=\dfrac{25}{8}\)
\(x=\dfrac{25}{8}-\dfrac{3}{10}\)
\(x=\dfrac{113}{40}\)
\(\dfrac{5}{7}+\dfrac{x}{35}=\dfrac{4}{5}\)
\(\dfrac{x}{35}=\dfrac{4}{5}-\dfrac{5}{7}\)
\(\dfrac{x}{35}=\dfrac{3}{35}\)
=>x=3