Geometry Practice Test 6

From point I, draw a perpendicular bisector on BC.
∠IDB = 90°
In ΔIDB,

∠BID+∠IDB+∠DBI = 180°
50° + 90° +∠DBI = 180°
DBI = 40°
⇒ ∠DBA = 80°
In ΔABC,
∠A +∠B+∠C = 180°
∠BAC+ 80° + 80° = 180°
∠BAC = 180° −160°
∠BAC = 20°