EQUIVALENT capacitance is the algebraic sum of all the reciprocal of the capacitance.1/Ceq = 1/C1 + 1/C2 + 1/C3 +...... (in series)Analysis: C1 = 9 μF, C2 = 18 μF \(C_{EQ} = \frac{18 \TIMES 9}{18+9} = 6 ~\MU F\)