Answer: Hello mate!
I guess here says:
125 = 5^x
and we want to express this equation in logaritmic form:
using the relation:
ln(a^b) = b*ln(a)
we can solve the previous equation for x as:
125 = 5^x
apply ln to both sides:
ln(125) = ln(5^x)
ln(125) = xln(5)
x = ln(125)/ln(5)