A propped cantilever has reactions: fixed end provides vertical reaction, horizontal reaction, and moment (3 unknowns); simple support provides vertical reaction (1 unknown) — total 4 unknowns. Available equilibrium equations: 3 (\(\sum F_x = 0\), \(\sum F_y = 0\), \(\sum M = 0\)). Degree of static indeterminacy \(= 4 - 3 = 1\). One compatibility equation (typically zero deflection at the prop) is needed to solve it.