Answer:
- 3log(10) -2log(5) ≈ 1.60206
 - no; rules of logs apply to any base. ln(x) ≈ 2.302585×log(x)
 - no; the given "property" is nonsense
 
Explanation:
1.
The given expression expression can be simplified to ...
 3log(10) -2log(5) = log(10^3) -log(5^2) = log(1000) -log(25)
 = log(1000/25) = log(40) . . . . ≠ log(5)
 ≈ 1.60206
Or, it can be evaluated directly:
 = 3(1) -2(0.69897) = 3 -1.39794
 = 1.60206
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2.
The properties of logarithms apply to logarithms of any base. Natural logs and common logs are related by the change of base formula ...
 ln(x) = log(x)/log(e) ≈ 2.302585·log(x)
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3.
The given "property" is nonsense. There is no simplification for the product of logs of the same base. There is no expansion for the log of a sum. The formula for the log of a power does apply:
 

Numerical evaluation of Mr. Kim's expression would prove him wrong.
 log(3)log(4) = (0.47712)(0.60206) = 0.28726
 log(7) = 0.84510
 0.28726 ≠ 0.84510
 log(3)log(4) ≠ log(7)