3.
a)
[tex]\frac{10}{x} = \frac{4}{5}\\\\Zal:\\x \neq o\\D = R \setminus\{0}\}\\\\4\cdot x = 10\cdot5\\\\4x = 50 \ \ /:4\\\\\boxed{x = 12,5}[/tex]
b)
[tex]\frac{1,5}{9} = \frac{x}{1,5}\\\\x\cdot 9 = 1,5\cdot1,5\\\\9x = 2,25 \ \ /:9\\\\\boxed{x =0,25}[/tex]
c)
[tex]\frac{24}{x}=\frac{3}{5}\\\\Zal:\\x \neq 0\\D = R \setminus\{0\}\\\\3\cdot x = 24\cdot5 \ \ /:3\\\\x = 8\cdot5\\\\\boxed{x = 40}[/tex]
d)
[tex]\frac{7}{0,2} = \frac{28}{x}\\\\Zal:\\x \neq 0\\D = R \setminus\{0\}\\\\7\cdot x = 28\cdot0,2 \ \ /:7\\\\x = 4\cdot0,2\\\\\boxed{x = 0,8}[/tex]
e)
[tex]\frac{3x}{5} = \frac{7}{3}\\\\3x\cdot 3 = 7\cdot5\\\\9x = 35 \ \ /:9\\\\x = \frac{35}{9}\\\\\boxed{x = 3\frac{8}{9}}[/tex]
f)
[tex]\frac{0,4}{5} = \frac{3x}{15}\\\\3x\cdot5 = 0,4\cdot15 \ \ /:15\\\\\boxed{x = 0,4}[/tex]
g)
[tex]\frac{x+1}{4} = \frac{3}{2}\\\\2(x+1) = 4\cdot3 \ \ /:2\\\\x+1 = 2\cdot3\\\\x =6-1\\\\\boxed{x = 5}[/tex]
h)
[tex]\frac{8}{3} = \frac{x-1}{5}\\\\3(x-1) = 8\cdot5\\\\3x-3 = 40\\\\3x = 40+3\\\\3x = 43 \ \ /:3\\\\x = \frac{43}{3}\\\\\boxed{x = 14\frac{1}{3}}[/tex]
i)
[tex]\frac{20}{x+2} = \frac{4}{0,3}\\\\Zal:\\x+2 \neq 0 \ \ \rightarrow \ \ x \neq -2\\D = R\setminus\{-2\}\\\\4(x+2) = 20\cdot0,3 \ \ /:4\\\\x+2 = 5\cdot0,3\\\\x = 1,5-2\\\\\boxed{x = -0,5}[/tex]
