Concept:
Points are collinear if slopes are equal.
Step 1: Write coordinates.
\[
A(60,3), B(40,-8), C(a,-52)
\]
Step 2: Slope AB.
\[
\frac{-8-3}{40-60} = \frac{-11}{-20} = \frac{11}{20}
\]
Step 3: Slope BC.
\[
\frac{-52+8}{a-40} = \frac{-44}{a-40}
\]
Step 4: Equate slopes.
\[
\frac{11}{20} = \frac{-44}{a-40}
\]
\[
11(a-40) = -880
\]
\[
a-40 = -80
\]
\[
a = -40
\]