5^(x+3)=2^x

5^(x+3)=2^x    take the log of both sides

log5^(x+3)= log2^x    and we can write

(x+3) log 5 = xlog 2    simplify

xlog5 +3log5 = xlog2     rearrange

xlog5 - x log2  = -3log5    factorthe left side

x(log5 - log2) = -3log5      divide both sides by (log5 - log 2)

x = -3log5 / (log5 - log 2)  =   -5.2694123920980896