In the given circle, radius is perpendicular to tangent.
So that means AB⊥AC
so ∠BAC =90°......(1)
Also we are given ∠ACB =71°................(2)
Now we will use angle sum property of a triangle here.
It states that sum of three angles of a triangle is 180° .
Applying this property here,
∠A +∠B +∠C =180°.............(3)
Plugging values from equation (1) and (2) in (3)
∠A +∠B +∠C =180°
90 +∠B +71 =180°
161 + ∠B = 180°
∠B = 19°
Answer: Angle ABC is 19 degrees.