Answer :
A sugestion: calculate m, c, d from:
3m + 4c + 7d = 5.45;
4m + 2c + 8d = 5.30;
2m + 5c + 6d = 5.15;
Then, calculate 10 - (4m + 2c + 9d);
3m + 4c + 7d = 5.45;
4m + 2c + 8d = 5.30;
2m + 5c + 6d = 5.15;
Then, calculate 10 - (4m + 2c + 9d);