PLEASE ANSWER IN DETAIL ( WILL GIVE BRAINLIEST )

GIVEN : magnitude of angle B = 68°

magnitude of angle C = 70°

So the value of angle A (interior) be A

We know A + angle B + angle C = 180° [ Sum of all three interior angles of a triangle = 180°]

=> A + 68° + 70° = 180° [By linear equation we can find the value of A]

=> A + 138° = 180°

=> A = (180 - 138)°

=> A = 42°

A(interior) + A(exterior) = 180° [ Sum of all adjacent angle on a straight line =180°]

42° + A(exterior) = 180°

=> A(exterior) = (180-42)°

=> A(exterior) = 138°

As because A(exterior) = x = 138° (ans)