2^{3x} = 7^{2-x}

2^{3x} = \dfrac{7^2}{7^x}

2^{3x} \cdot 7^x =49

(2^3)^x\cdot 7^x = 49

(8\cdot 7 )^x = 49

56^x = 49

\log56^x = log49

x\log56 = \log49

x = \dfrac{\log49}{\log56}