Answer:
∠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