Question

$3*5^{x+3}+2*5^{x+1}=77$

Answer 1

$3*5^{x+3}+2*5^{x+1}=77 \ \ 5^{x+1}=t \ \ 75t+2t=77 \ \ 77t=77 \ \ t=1 \ \ 5^{x+1}=1 \ \ x+1=0 \ \ x=-1$