Tìm (x), biết:

a) \(12 + x =  - 37\)

\(x =  - 37 - 12\)

\(x =  - 49\)

Vậy \(x =  - 49\).

\(\left( {25 - x} \right):3 = 9 - 8\)

\(\left( {25 - x} \right):3 = 1\)

\(25 - x = 3\)

\(x = 22\)

Vậy \(x = 22\).

c) \(9 + \left( {5x - 10} \right) = 4\)

\(5x - 10 = 4 - 9\)

\(5x - 10 =  - 5\)

\(5x =  - 5 + 10\)

\(5x = 5\)

\(x = 1\)

Vậy \(x = 1\).

d) \({5.3^{1 - x}} + {3^{1 - x}} = 162\)

\[{3^{1 - x}}.\left( {5 + 1} \right) = 162\]

\[{3^{1 - x}}.6 = 162\]

\[{3^{1 - x}} = 27\]

\({3^{1 - x}} = {3^3}\)

Suy ra \(1 - x = 3\)

\(x =  - 2\)

Vậy \(x =  - 2\).