Answer
$20.8$ $g$ $F$
Work Step by Step
Each percentage represents the number of grams of an element per 100.0 grams of that compound. Use this as a conversion factor.
$55.8 g$ $CuF_{2}$$\times\frac{37.42 g F}{100.0 g CuF_{2}}$ $=20.8$ $g$ $F$