Question 551128
first, we need to know
1. if a^2+b^2=c^2, then the triangle is a right triangle because of pythagorean thereorm. (i didn't spell that correctly)

2. if a^2+b^2>c^2, then the triangle is acute

3. if a^2+b^2<c^2, then the triangle is obtuse
a=18,b=20,and c=27
c^2=729
a^2+b^2=724
a^2+b^2<c^2 is satisfied so the given angle is "obtuse" angle.