Problem 1)
The base of the exponential is 12 which is also the base of the log as well. The only answer choice that has this is choice B.
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Problem 2)
log(x) + log(y) - 2log(z)
log(x) + log(y) - log(z^2)
log(x*y) - log(z^2)
log[(x*y)/(z^2)]
Answer is choice D
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Problem 3)
log[21/(x^2)]
log(21) - log(x^2)
log(21) - 2*log(x)
This matches with choice B
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Problem 4)
Ln(63) = Ln(z) + Ln(7)
Ln(63)-Ln(7) = Ln(z)
Ln(63/7) = Ln(z)
Ln(9) = Ln(z)
z = 9
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Problem 5)
Ln(5x-3) = 2
5x-3 = e^2
5x = e^2+3
x = (e^2+3)/5
This means choice A is the answer
