Question

how to solve this?? ​

Answer 1

Answer:

$11 + 7 = 18 \\ \frac{1}{r} = \frac{1}{18} + \frac{1}{9} \\ = \frac{1 + 2}{18} \\ = \frac{1}{6} \\ r = 6$

Answer 2

Answer:

6

Explanation:

11and7are in series combination

11+7=18

then now 9and18are in parallel combination

9×18/9+18=6