We will use the property of logarithms that ln(a^x) = xln(a)
With that:
3.14159^x = 4
=> ln(3.14159^x)=ln(4)
=> xln(3.14159)=ln(4)
:. x=ln(4)/ln(3.14159)
Note that this is eqivalent to the base 3.14159 log of 4, a result we could have also found by taking the base 3.14159 log of both sides and applying log_a(a^x)=x