Let amount of 3 types of rice be x,y and z, respectively.
Using rule of alligation for x and y
So, x : y = 12 : 84 = 1 : 7
Similarly using the rule of alligation x and z
So, x : z = 132 : 84
= 11 : 7
= 1 : 7/11
On combining the two ratio, we get
x : y : z = 1 : 7 : 7/11
= 11 : 77 : 7