A little Algebra, and we're home free!
We are given R = 20 and r2 = 75. We need to find r1.
The formula is 1/R = 1/r1 + 1/r2. Plug-in:
1/20 = 1/r1 + 1/75
1/20 - 1/75 = 1/r1
0.0366 = 1/r1
r1 = 1/0.03666
r1 = 27.272
Our answer is r1 = 27 ohms.
Answer:
5
Step-by-step explanation:

Answer:
Ted
Step-by-step explanation:
B is the correct answer I think