How do you defeat elite four bertha?

Elite Four Bertha Squad Quagsire female Lv.55 Water/Ground weak against GRASS Hippowdon female Lv.59 Ground weak against WATER, Grass, Ice Whiscash female Lv.55 Water/Ground weak against GRASS Golem female Lv.56 Rock/Ground weak against WATER, GRASS, Ice, Fighting, Ground, Steel Sudowoodo female Lv.56 Rock weak against WATER, GRASS, Fighting, Ground, Steel