70 ohms is the answer.
I think you are mixing up Total Resistance of loads in series with the Equivalent Resistance of loads in parallel.
Series circuit: total resistance is the sum of all resistances (loads) in the circuit.
Parallel circuits: equivalent resistance will always be less than the smallest of the resistances, and can be calculated with the formula
Req = 1/(1/R1 + 1/R2 +…)
Equivalent resistance is a way of taking two or more parallel loads/circuits and combining them into one theoretical resistance. It lets you know what the resistance of those parallel circuits are from the perspective of the power supply.