In Fig. 2.14, points lying in the interior of the triangle PQR are _____, that in the exterior are _____ and that on the triangle itself are _____.

Interior: O, S, Exterior: T, N, On triangle: P, Q, R, M
Step 1: Look at triangle PQR. The triangle has a boundary (its three sides) and three corner points (vertices): P, Q, R.
Step 2: Meanings.
Step 3: Check each point.
Result: Interior = O, S. Exterior = T, N. On the triangle = P, Q, R, M.