Bài 1: \(\dfrac{5}{9}=\dfrac{20}{36}\)
=>\(\dfrac{5}{20}=\dfrac{9}{36}\); \(\dfrac{9}{5}=\dfrac{36}{20};\dfrac{20}{5}=\dfrac{36}{9}\)
Bài 2:
a: \(\dfrac{x}{18}=\dfrac{-33}{54}\)
=>\(\dfrac{x}{18}=\dfrac{-11}{18}\)
=>x=-11
b: \(\dfrac{-15}{x}=\dfrac{3}{7}\)
=>\(x=\dfrac{-15\cdot7}{3}\)
=>\(x=-5\cdot7=-35\)
c: \(\dfrac{x+1}{24}=\dfrac{-5}{8}\)
=>\(x+1=-\dfrac{5}{8}\cdot24=-15\)
=>x=-15-1=-16
d: \(\dfrac{28}{-77}=\dfrac{-4}{2x+1}\)
=>\(\dfrac{28}{77}=\dfrac{4}{2x+1}\)
=>\(\dfrac{4}{2x+1}=\dfrac{4}{11}\)
=>2x+1=11
=>2x=10
=>x=5
e: \(1,8:x=1,5:\dfrac{5}{3}\)
=>\(1,8:x=1,5\cdot\dfrac{3}{5}=0,9\)
=>x=1,8:0,9=2
g: \(0,75:1,2=x:1,8\)
=>\(x:1,8=\dfrac{5}{8}\)
=>\(x=\dfrac{5}{8}\cdot1,8=\dfrac{5}{8}\cdot\dfrac{9}{5}=\dfrac{9}{8}\)