Tìm x, biết: a) x:8/5 = 5/2 

a) \(x:\frac{8}{5} = \frac{5}{2}\)

 \(x = \frac{5}{2} \cdot \frac{8}{5}\)

 \(x = 4\)

Vậy \(x = 4.\)

b) \( - 0,6 + x = 0,5\)

\(x = 0,5 - \left( { - 0,6} \right)\)

\(x = 0,5 + 0,6\)

\(x = 1,1.\)

Vậy \(x = 1,1.\)

c) \(\left( {5 - 4x} \right)\left( {\frac{5}{4}x - 2} \right) = 0\)

\[5 - 4x = 0\] hoặc \(\frac{5}{4}x - 2 = 0\)

Trường hợp 1:

\[5 - 4x = 0\]

\(4x = 5\)

\(x = \frac{5}{4}\)

Trường hợp 2:

\(\frac{5}{4}x - 2 = 0\)

\(\frac{5}{4}x = 2\)

\(x = 2:\frac{5}{4}\)

\(x = \frac{8}{5}.\)Vậy \(x \in \left\{ {\frac{5}{4};\,\,\frac{8}{5}} \right\}.\)