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Mình chỉ làm được vài câu thôi:
II: Tự luận
Bài 1:
a: \(\dfrac{9}{x}=\dfrac{25}{12}\)
=>\(x=9\cdot\dfrac{12}{25}\)
=>\(x=\dfrac{108}{25}\)
b: \(1\dfrac{1}{4}:x=2\dfrac{1}{4}:1\dfrac{1}{3}\)
=>\(\dfrac{5}{4}:x=\dfrac{9}{4}:\dfrac{4}{3}\)
=>\(\dfrac{5}{4}:x=\dfrac{9}{4}\cdot\dfrac{3}{4}=\dfrac{27}{16}\)
=>\(x=\dfrac{5}{4}:\dfrac{27}{16}=\dfrac{5}{4}\cdot\dfrac{16}{27}=\dfrac{80}{108}=\dfrac{20}{27}\)
Bài 2:
a: \(\dfrac{4}{9}:x=3\dfrac{1}{3}:2,25\)
=>\(\dfrac{4}{9}:x=\dfrac{10}{3}:\dfrac{9}{4}=\dfrac{10}{3}\cdot\dfrac{4}{9}=\dfrac{40}{27}\)
=>\(x=\dfrac{4}{9}:\dfrac{40}{27}=\dfrac{4}{9}\cdot\dfrac{27}{40}=\dfrac{3}{10}\)
b: \(\dfrac{49}{x-3}=\dfrac{7}{2}\)
=>\(x-3=49\cdot\dfrac{2}{7}=14\)
=>x=14+3
=>x=17
c: \(\dfrac{x-3}{5}=\dfrac{5-2x}{11}\)
=>\(11\left(x-3\right)=5\left(5-2x\right)\)
=>11x-33=25-10x
=>21x=58
=>\(x=\dfrac{58}{21}\)