Of the first graders who were asked, 1/6 like math best, 2/3 like reading best, and 12 like science best. How many first graders were asked their favorite subject? Into how many equal parts should the picture be divided?

2/3 = 4/6 (reading) + 1/6 (math) = 5/6 (reading/math)

6/6 - 5/6 = 1/6 (science) = 12 kids

12 kids = 1/6, 12*6 = 72 kids total