Question

m DXB = 70° 15' 12", m DXC = 30° 30' 20" m CXB

Answer 1

Sum of all angles of a triangle is = 180 degrees
Hence,

m∠DXB+m∠DXC+m∠CXB=180°00′00"


→m∠CXB=180°00′00"−(m∠DXB+m∠DXC)

→m∠CXB=180°00′00"−(70°15′12"+30°30′20")

→m∠CXB=180°00′00"−100°45′32"

→m∠CXB=79°14′28"
is the required answer.