Đáp án:

$\begin{array}{l}
1)x:8 = 5:4\\
 \Rightarrow \frac{x}{8} = \frac{5}{4}\\
 \Rightarrow x = \frac{{8.5}}{4} = 20\\
\text{Vậy}\,x = 20\\
2)\left( {x - 1} \right):1,5 = 2,8:0,5\\
 \Rightarrow \frac{{x - 1}}{{1,5}} = \frac{{2,8}}{{0,5}}\\
 \Rightarrow x - 1 = \frac{{2,8.1,5}}{{0,5}}\\
 \Rightarrow x - 1 = 2,8.3\\
 \Rightarrow x - 1 = 8,4\\
 \Rightarrow x = 1 + 8,4\\
 \Rightarrow x = 9,4\\
\text{Vậy}\,x = 9,4\\
3)2,5:7,5 = x:\frac{3}{5}\\
 \Rightarrow \frac{{2,5}}{{7,5}} = x:0,6\\
 \Rightarrow \frac{1}{3} = \frac{x}{{0,6}}\\
 \Rightarrow x = \frac{{0,6}}{3}\\
 \Rightarrow x = 0,2\\
\text{Vậy}\,x = 0,2\\
4)0,6:x = x:2,4\\
 \Rightarrow \frac{{0,6}}{x} = \frac{x}{{2,4}}\\
 \Rightarrow x.x = 0,6.2,4\\
 \Rightarrow {x^2} = 1,44\\
 \Rightarrow \left[ \begin{array}{l}
x = 1,2\\
x =  - 1,2
\end{array} \right.\\
\text{Vậy}\,x = 1,2;x =  - 1,2\\
5)2\frac{2}{3}:x = 1\frac{7}{9}:0,2\\
 \Rightarrow \frac{8}{3}:x = \frac{{16}}{9}:\frac{1}{5}\\
 \Rightarrow x = \frac{8}{3}.\frac{1}{5}:\frac{{16}}{9}\\
 \Rightarrow x = \frac{8}{{15}}.\frac{9}{{16}}\\
 \Rightarrow x = \frac{3}{{5.2}}\\
 \Rightarrow x = \frac{3}{{10}}\\
\text{Vậy}\,x = \frac{3}{{10}}\\
6)2,5:4x = 0,5:0,2\\
 \Rightarrow 4x = 2,5.0,2:0,5\\
 \Rightarrow 4x = 0,5:0,5\\
 \Rightarrow 4x = 1\\
 \Rightarrow x = \frac{1}{4} = 0,25\\
\text{Vậy}\,x = 0,25\\
7)\frac{1}{5}x:3 = \frac{2}{3}:0,25\\
 \Rightarrow \frac{1}{5}x = \frac{2}{3}.3:0,25\\
 \Rightarrow \frac{1}{5}x = 2:0,25\\
 \Rightarrow \frac{1}{5}x = 8\\
 \Rightarrow x = 8.5 = 40\\
\text{Vậy}\,x = 40\\
8)1,25:0,8 = \frac{3}{8}:0,2x\\
 \Rightarrow 0,2x = \frac{3}{8}.0,8:1,25\\
 \Rightarrow 0,2x = 0,3:1,25\\
 \Rightarrow 0,2x = 0,24\\
 \Rightarrow x = 0,24:0,2
\end{array}$

=> x=1,2

Vậy x=1,2