Answer: m∠S = 19°
Step-by-step explanation:
We know the angles of a triangle add up to 180° (and if you don't, you do now)
-> We are given one angle, 142°
-> We are given the fact this is an isosceles triangle, or one with two congruent sides
[] This means the other two angles are congruent
-> Taking this information, we will set up an equation to solve for x
180° = 142° + 2x°
38° = 2x
19° = x
x = 19°
x = m∠S, so m∠S = 19°
m∠S = 19°