Question

find the unknown angles and state angle sum property​

Answer 1

Answer:

x+x+40 = 180 degree

2x=140

x=70 degree

angle sum property is that sum of all angles of triangle is 180 degree

Answer 2

$\large\mathfrak{{\pmb{{\underline{Given}}:}}}$

In ∆ ABC, $\sf\Large\angle A = 40° \\\\\:\:\:\:\:\:\:\angle B = \angle C = x° \\\\\: By \: angle \: sum \: property, \\\\\angle A + \angle B + \angle C = 180°\\\\\implies\: 40° + x° + x° = 180°\\\\\implies\: 2x° = 140° \\\\\implies\: x° =\dfrac{140}{2} \\\\\implies{\boxed{x = 70°}}$

$\Large\pink{\underline{Angle \: sum \: property}: }$

It states that the sum of the angles of a triangle is 180°.

$\pink{Hope \: it \: helps}$