We infer from the given diagram that the same pattern is followed after every 10ohm resistor. The infinite pattern in parallel as a whole is considered as to be Rx.
Thus, Rx = R + (R||Rx)
Solving for Rx, we get Rx = 1.62R, where R=10ohm.
So we have Rx = (1.62ohm)*(10ohm), which gives Rx=16.2ohm
Therefore, Req = 5 + (10||16.2)
=> 5 + [(10*16.2)/(10+16.2)] => Req = 5 + (162/26.2) which gives Req=11.18 ohm.