Answer:
12. 0.9045
15. 0.4157
Step-by-step explanation:
These are solved by taking logarithms, then solving the resulting linear equation. The applicable rule of logs is ...
log(a^b) = b·log(a)
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12. (x+1)log(8.2) = log(55) . . . . . take the log of both sides
x +1 = log(55)/log(8.2) . . . . . . divide by log(8.2)
x = log(55)/log(8.2) -1 = 1.9045 -1 = 0.9045
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15. (2x)log(72) = log(35 . . . . . . . take the log of both sides
x = log(35)/(2·log(72)) . . . . . . . divide by the coefficient of x
x ≈ 0.4157
