(1/8) ​x+3 =16 2x-1

(1/8)^x+3 = 16^2x-1

 

1/8 = 2^-3      and      16 = 2⁴ 

 

Substitute.

(2^-3)^x+3 = (2⁴)^2x-1

 

2^-3x-9 = 2^8x-4

 

Now that the bases are the same,

we can just set the exponents equal to each other.

-3x - 9 = 8x - 4

 

-9 = 11x - 4

 

-5 = 11x

 

x = -5/11     :)