The sum of the interior angles in a triangle is 180^o

Find x

70 + 80 + x = 180

150 + x = 180

(-150) (-150)

x = 30^o

Isosceles triangle

this triangle has: 2 equal sides and 2 equal interior angles

180 – 30 = 150^o

x = 150 2 (2 equal angles)

x = 75^o

Right angled triangle

a + b = 90^o

Equilateral triangle

This triangle has: 3 equal sides and 3 equal interior angles of 60^o each