Question

4. An equilateral triangle and an isosceles triangle share a common side. What is the measure of ∠ A B C?

Answer 1

∠ABC = 98°

Explanation:

an isosceles triangles base angles have the same angle measures

so both are 71

add them and then subtract that from 180 to find ∠ABD

180 - (71 + 71)

180 - 142 = 38

that is ∠ABD

to find ∠ABC you must add ∠DBC to ∠ABD

all angles of an equilateral triangle are equivalent

they are also 60 degrees

so add 60 to 38

38 + 60 = 98

that is your answer