Answer:
R_eq = 6 Ω
Step-by-step explanation:
In a series circuit the current is constant throughout the circuit and the resistance is the sum of all the resistances in it.
R_eq = ∑
in this case we have
R_eq = R₁1 + 3 R₂
where R₁ is the resistance of the fan and R₂ the resistance of each light, we must clarify that we will assume that the resistance of the lights does not change with temperature
let's calculate
R_eq = 3 + 3 1
R_eq = 6 Ω