Question

the resistance of parallel circuit consisting of 2 branches is 12 ohms.if the resistance of one branch 18 ohms,what is the resistance of the order?

Answer 1

1/R = 1/r1 + 1/r2
1/12 = 1/18 + 1/x
1/x = 1/12-1/18
1/x = 3-2/36
1/x = 1/36
x = 36

36 is the resistance