book Maths Puzzle Numerical Ability

write as a logarithm of a single number:

2lna+7lnb-3lnc-lnd

a= ln(14ab/3cd)
b= ln(14abd/3c)
c= ln(a^2b^7d/c^3)
d= ln(a^2b^7/c^3d)

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book Other Question

I have been working on this problem for a week and I still can't figure it out. This is what I have so what am I doing wrong?

Let the function f be defined by f(x) = 1/(sqrt1-x What is the answer to 5^2x = 8?