Since this question is asking for how many wizards are in magic club, we can represent wizards with the variable "w"
w = wizards
Next, we know that there are 120 goblins and that there are 20% more goblins than wizards in magic club.
120 = w + 20%w
120 = w + 0.2w
(percentages are just the percent/100)
120 = 1.2w
1200 = 12w
100 = w
Final Answer: There are 100 wizards in the magic club