Nomor 19 bantuin ya... Sekalian caranya

A = 180-100 =80
C = 180-85 = 95
95+80 = 175°
ABC = 180-175 = 5°

<ACB = 180°-85° =95° (Berpelurus)
<BAC = 180°-100° =80° (Berpelurus)

<ABC = 180°-(95°+80°)
=====> 180°-175°
=====> 5°