B. 60 this can be answered by also knowing degree angle's as it starts at 0 increments of 10
Step-by-step explanation:

If two angles and included side of one triangle are equal to two angles and the included side of the other triangle , then the two triangles are congruent (ASA rule).
in figure
- consider triangle ABD and ACD
- Angle BAD = angle CAD
- AB = AC
- Angle B = angle C
- triangle ABD congruent to Triangle ACD ( by ASA rule)