Question 1006757
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You just need to learn that the definition of logarithm is

{{{A=B^C}}} is equivalent to {{{C=log(B,A)}}}
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A) 5^x=7
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{{{7=5^x}}} is equivalent to {{{x=log(5,7)}}}
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B) 9^(x/3)=13
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{{{matrix(2,1,"",13=9^(x/3))}}} is equivalent to {{{x/3=log(9,13)}}}, or {{{x=3log(9,13)}}} 
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C) 2^(x+4)=3
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{{{3=2^(x+4)}}} is equivalent to {{{x+4=log(2,3)}}}, or {{{x=log(2,3)-4}}}

Edwin</pre>