Tìm (x), biết:

a) \(5x - {2^3} = {3^3}\)

\(5x - 8 = 27\)

\(5x = 35\)

\(x = 7\)

Vậy \(x = 7\).

b) \(51 - 3\left( {x + 2} \right) = 60\)

\(3\left( {x + 2} \right) = 51 - 60\)

\(3\left( {x + 2} \right) =  - 9\)

\(x + 2 =  - 3\)

\(x =  - 5\)

Vậy \(x =  - 5\).

c) \({3^{x + 2}} + {3^x} = 10\)

\({3^x}{.3^2} + {3^x} = 10\)

\({3^x}.\left( {{3^2} + 1} \right) = 10\)

\({3^x}.10 = 10\)

\({3^x} = 1\)

\({3^x} = {3^0}\)

Suy ra \(x = 0\).

Vậy \(x = 0\).