To go from exponential to logarithmic, you can use \(e^x=y\) (exponential) => \(log_{e} (y)=x\) (logarithmic). With your specific equation, this would make \(7^5=16,807\) => \(log_7(16,807)=5\), with that being your logarithmic form.
the last digit (1s place; just to the left of the decimal dot) recurs after the power is 4+. 7⁰⁺⁴ⁿ all have the last digit as '1'. 7¹⁺⁴ⁿ have the last digit as '7'. 7²⁺⁴ⁿ have the last digit as '9'. 7³⁺⁴ⁿ have the last digit as '3'. 7⁴⁺⁴ⁿ, the same as 7⁰⁺⁴ⁿ have the last digit as '1'. replace the 7 with 16 in the expression. 807
