Answer :

[tex]20 \frac{3}{4}= \frac{83}{4} \\ \\ 180^{(4}-\frac{83}{4}= \frac{720-83}{4}=\boxed{\frac{637}{4}=159 \frac{1}{4}-the \ suplement}[/tex]
[tex]supplement = 20 \ 3/4 + x =180 \\20 \ 3/4 + x =180 \\x = 180 - 20 \ 3/4 \\\boxed{x = 159.25}[/tex]