1. Algebra help

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What is the PF?

2. Re: Algebra help

Let's start by filling in the values. SO
$19=9(\frac{1}{1-\frac{Pf}{478}})$
Simplifying
$19=9(\frac{1}{\frac{478-Pf}{478}})$
$19=9(\frac{478}{478-Pf})$
$19=(\frac{4302}{478-Pf})$
After this we cross-multiply. and solve for Pf.