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To solve the following:
1.21 = (1.1)^n
You know that the inverse of exponentiation is the logarithm, so take the log (base 10) or ln (base e) or whatever base of both sides.  For fun we'll take it to base 10.

log(1.21) = n * log(1.1)
now divide both sides by log(1.1) to get:
log(1.21)/log(1.1) = n
Use your calculator to divide log(1.21) by log(1.1) and find the result "2",  So...
n = 2
The trick here is to know that when you take the log(a^n) you get n * log(a).  You can then  divide by log(a) to get "n" by itself.

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