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oobleck it is very hard to parse what you typed, so I'll guess you meant
log( 75÷16) - 2 log2(4√'25÷81)^3 3√ (25÷81)+1÷3 log3(215 ÷3-15)
log91 - 6log2(101) 3√106) + 1 + 3log3(203)
since you have logs to various bases, and that cryptic middle term, I'm lost here.
It's not my job to figure out what you mean.
It's your job to say it so clearly you cannot be misunderstood.