Question

preciso da resposta da letra c

Answer 1

$10^{-3x+21} = 1000000000^{x-3} \\\\10^{-3x+21}=10^{9(x-3)} \\\\-3x+21=9(x-3)\\\\-3x+21=9x-27\\\\9x+3x=21+27\\\\12x=48\\\\x=\frac{48}{12} \\\\x=4$

Espero ter ajudado!