Question

 2^{3+x} = 0.4* 5^{3+x}

Answer 1

$2^{3+x} = 0.4* 5^{3+x}$
$2^{3}*2^{x} = 0,4* 5^{3}*5^{x}$
$frac{ 2^{3}}{0,4* 5^{3}} = frac{5^x}{2^{x}}$
$( frac{5}{2})^{-2} = (frac{5}{2})^x$
$x = -2$

Answer 2

2^{3+x} = 0.4* 5^{3+x} 
8*2^x=2/5*5^3*5^x
2^x/5^x=5^2/2^2
(2/5)^x=(5/2)^2=(2/5)^-2
x=-2