If
20 % 5 = 24

21 % 7 = 33

42 % 6 = 67

Then;

66 % 6 = ?

1211
The number on the right side is formed as (sum of digits of the 1st number)(number1/number2)
example,
20 % 5 = 24 (2+0)(20/4)
21 % 7 = 33 (2+1)(21/7)
42 % 6 = 67 (4+2)(42/6)

Simillarly,
66 % 6 = 1211 (6+6)(66/6)