OK, I really don't know how to help you now using this medium. You claim to have watching the Khan Academy video, but this question is answered in that. The s

OK, I really don't know how to help you now using this medium. You claim to have watching the Khan Academy video, but this question is answered in that. The simple rules are these: log(a.b) = log(a) + log(b) hence log(a^4) = log(a.a.a.a) = log(a)+log(a)+log(a)+log(a) = 4.log(a) Therefore if a = b^z then log(a) = log(b^z) so log(a) = z.log(b) This is true for all bases. Then we have log_b(b) = 1 : Log (base b) of b is 1. Hence log_b(b^2) = 2 log_b(b^3) = 3 and so on. In all this the basic rule is this: if x = b^y then log_b(x) = log_b(b^y) = y.log_b(b) = y So if the base is 10, then we have: If a = 10^b then log(a) = log(10^b) = b.log(10) = b.1 = b So now, start with the equation t=log(u), assuming the log is base 10, and use the above rules to change it around. When you do that, see if you can get to saying u equals something. Finally, you need to study sections 1, 2 and 3 of this page: http://en.wikipedia.org/wiki/Logarithm http://en.wikipedia.org/wiki/Logarithm What's on that page will also help you to understand the questions.