What is the mole ratio of d to a in the generic chemical reaction 2a+b-- c+3d?

 D : A is 3 : 2.

Explanation:

The law of definite proportion is being used here. The law states that a given compound always has the same proportion of its constituent elements by mass

Keeping in mind law and equation:

2a + b = c + 3d

using the ratio of Stoichiometric coefficients:

This means that from two moles of "a" forms three moles of "d"  

So the ratio of d:a is 3:2

level 4 to level 2 : ))