Answer
About $31.5$lb of his body weight is fat.
Work Step by Step
Typical percentage problem:
What percent ($n$, as a decimal number) of (the base amount $y)$ is $x?$
Translated:$\quad n\cdot y=x$
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Here, reworded, $\quad 16.5\%$ of ($y=191$) is ($x=?$).
Translated:$\quad 0.165\cdot 191=x$
($ 16.5\%$ converted to decimal notation is $0.165)$
$x=31.5$lb
