c: \(1\dfrac{5}{15}\cdot0,75-\left(\dfrac{11}{20}+25\%\right):\dfrac{-3}{5}\)
\(=\dfrac{4}{3}\cdot\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{5}{20}\right)\cdot\dfrac{-5}{3}\)
\(=1+\dfrac{5}{3}\cdot\dfrac{16}{20}\)
\(=1+\dfrac{5}{3}\cdot\dfrac{4}{5}=1+\dfrac{4}{3}=\dfrac{7}{3}\)
Bài 1:
a: \(\dfrac{2}{3}-\dfrac{1}{2}x=\dfrac{3}{4}\)
=>\(\dfrac{1}{2}x=\dfrac{2}{3}-\dfrac{3}{4}=\dfrac{8-9}{12}=\dfrac{-1}{12}\)
=>\(x=-\dfrac{1}{12}\cdot2=-\dfrac{1}{6}\)
b: \(\dfrac{-x}{3}=2\dfrac{1}{7}:\dfrac{5}{7}\)
=>\(\dfrac{x}{-3}=\dfrac{15}{7}\cdot\dfrac{7}{5}=3\)
=>\(x=-3\cdot3=-9\)
c: \(\dfrac{5}{4}+\dfrac{1}{4}:x=1\dfrac{3}{8}\)
=>\(\dfrac{1}{4}:x=1+\dfrac{3}{8}-\dfrac{5}{4}=\dfrac{11}{8}-\dfrac{5}{4}=\dfrac{1}{8}\)
=>\(x=\dfrac{1}{4}:\dfrac{1}{8}=\dfrac{1}{4}\cdot8=2\)
d: \(\left(3,5-2x\right)\cdot1\dfrac{1}{3}=-20\%\)
=>\(\left(3,5-2x\right)\cdot\dfrac{4}{3}=-\dfrac{1}{5}\)
=>\(3,5-2x=-\dfrac{1}{5}:\dfrac{4}{3}=\dfrac{-3}{20}=-0,15\)
=>2x=3,5+0,15=3,65
=>\(x=\dfrac{3.65}{2}=1,825\)
e: \(\dfrac{5^x}{125}=5\)
=>\(5^x=125\cdot5=625\)
=>x=4
