HKIMO 2026 THPT (Grades 10–12 shared) National Final (Heat) Set 05 Question 20

In the figure, $TA$ and $DC$ are tangent to the circle at $A$ and $C$. Points $T,B,C$ are collinear in that order. Given $\angle ATB=50^\circ$ and $\angle BCD=75^\circ$, find $\angle ABC$ in degrees.