Answer:
I = 11/2 = 5.5
R = 60/11 ≈ 5.5Ω
Explanation:
You use V = I·R twice.
Entire circuit: 140 = I·(20+R)
Resistor: 30 = I·R
Solving this system of equations gives:
140 = I·(20+R) = 20I + IR
30 = I·R
140 = 20I + 30
20I = 110
I = 11/2 = 5.5
R = 60/11 ≈ 5.5Ω
