Answer:
The third angle measures 80°
Step-by-step explanation:
Let us solve the question
In any triangle
∵ The sum of the measures of the interior angles of a triangle is 180°
∵ The angle of triangles are ∠1, ∠2, and ∠3
∴ m∠1 + m∠2 + m∠3 = 180°
∵ Two of the angles of the triangle are 30° and 70°
∴ m∠1 = 30°
∴ m∠2 = 70°
→ Substitute them in the rule above
∴ 30° + 70° + m∠3 = 180°
→ Add the like terms
∵ (30 + 70) + m∠3 = 180
∴ 100 + m∠3 = 180
→ Subtract 100 from both sides
∵ 100 - 100 + m∠3 = 180 - 100
∴ m∠3 = 80°
∴ The third angle measures 80°
