107 Adult tickets were sold.
Total tickets sold = 428
428÷4=107 (split into four equal groups)
107×3=321 (amount of student tickets sold) (this is 3/4 of the total amount sold)
107×1=107 (amount of adult tickets sold) (this is 1/4 of the total amount sold)
321+107=428 (amount of tickets sold total)
321 (amount of student tickets sold) is three times the number of adult tickets sold. (107) 107×3=321
