1. The problem statement, all variables and given/known data We're working with logarithms of base 3, and log(4)=a and log(7)=b. The goal is to put log(21) in terms of a and b. For example, take the log(112). It's the same thing as 2a+b since 4*4*7 = 112. 2. Relevant equations Just the standard log properties. 3. The attempt at a solution The only thing I could come up with is 1 + b log(3) = 1. I've been using Matlab to try to figure out a way to create 21 using a product and/or quotient of powers of 7 and 3 but have been unable to do so.