since we know that they lose 71%, what's left on the dry apple is then 100% - 71% = 29%, so the dry apple only has 29% of the original weight.
now, if we want to get 128 lbs of dry apple, that means that 128 will be the 29%, how much will then be the 100%, let's say is "x" then.
![\bf \begin{array}{ccll} \stackrel{dry~apple}{lbs}&\%\\ \cline{1-2} 128&29\\ x&100 \end{array}\implies \cfrac{128}{x}=\cfrac{29}{100}\implies 12800=29x \\\\\\ \cfrac{12800}{29}=x\implies 441.38\approx x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/cg7fmt1ep0edfikjbd6o91ufmy2cnxozco.png)