How to find a total resistance of the circuit

To find the total resistance of the circuit:

They are 2 ways to get that (you can use both methods for 1 exercise)

1 - If resistances are series, just add together.

Rt = R1 + R2

2 If are parallel, do the same thing but the inverse of each resistance.

Rt = 1/R1 + 1/R2