Задание 606

$$3^{4x+21}=27^{2x}$$

$$3^{4x+21}=3^{3\cdot 2x}$$

$$3^{4x+21}=3^{6x}$$

$$4x+21=6x$$

$$6x-4x=21$$

$$2x=21$$

$$x=\dfrac{21}2=10,5$$