How to solve resistors in parallel and series?
We start furthest from the power inputs. The orange box has the first two. They are in series. So we add them
R34 = R3 + R4
R34 = 1kΩ + 1kΩ = 2kΩ
Now we move on to the next two
The next orange box has the two resistors in parallel
1/R234 = 1/R2 + 1/R34
1/R234 = 1/1kΩ + 1/2kΩ
1/R234 = 1 + 1/2 = 3/2
R234= 0.67kΩ
The last two resistors are in series
RTotal = R1 + R234
RTotal = 1kΩ + 0.67kΩ = 1.67kΩ