In the second step of this reaction, isocyanic acid reacts to form melamine and carbon dioxide: HNCO(l)→C3N3(NH2)3(l)+CO2(g) Balance this reaction and enter the coefficients below.

The coefficients are 6, 1, 3

Explanation:

HNCO →C3N3(NH2)3 + CO2

From the above equation, there are a total of 6 atoms of nitrogen on the right side and 1atom on the left. It can be balance by putting 6 in front of HNCO as shown below:

6HNCO → C3N3(NH2)3 + CO2

Now there are 6 atoms of carbon on the left side and 4 atoms on the right side. It can be balance by putting 3 in front of CO2 as shown below:

6HNCO → C3N3(NH2)3 + 3CO2

Now the equation is balanced as the numbers of atoms of the different elements on both sides of the equation are the same.

The coefficients are 6, 1, 3

i think it's letter a.