Which one of the following four interchanges in signs and numbers would make the given equation correct?

9 ÷ 15 x 12 = 20

 ÷ and x, 12 and 9

1. Considering each case separately-
   a) Making the interchanges given in 1, we get 9 x 12  ÷ 15 = 20; 7.2 = 20, which is false.
   b) Making the interchanges given in 2, we get 15 x 9  ÷ 12 = 20; 11.25 = 20, which is false.
   c) Making the interchanges given in 3, we get 12 x 15  ÷ 9 = 20; 20 = 20, which is true.