log (x/y) = log(x) - log(y)
log(x*y) = log(x)+log(y)
log(x^y) = y*log(x)
log(10) = 1. Log is log base 10. And log base n of n = 1.
Use those log properties to solve this problem.
log(9/20) = log(9) - log(20) = log(3^2) - log(2*10) = 2*log(3) - (log(2) +log(10)) = 2b - (a+1) = 2b-a-1
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