in this combination if u carefully observe 2 resistors are in parallel with one of them in series and moreover the fourth one is parallel to all three
now, total resistance of two parallel resistors =110+110=5ohm
now this combination is in series with another =5+10=15ohm
finally this combination is on parallel with 4th resistor =115+110
=230+330=530=16
=6 ohm
hence equivalent resistance is 6 ohm