Answer:
Total cereal mixture is 5·7 kg
Explanation:
A cereal mixture contains in rice , wheat and corn 
In a ratio of rice, wheat and corn is 

let the number be x 
Rice 
 3x
 3x
Wheat 
 7x
 7x
Corn 
 9x
 9x
Total cereal mixture is 19x
Wheat 
 2·1 kg
 2·1 kg
So, Wheat 7x equals to 2·1 kg
7x 
 2·1 kg
 2·1 kg
x 
 kg
 kg
x 
 0·3 kg
 0·3 kg
Total cereal mixture is 19x
19 ₓ 0·3 
 5·7 kg
 5·7 kg