Answer:
3; Double Displacement
Step-by-step explanation:
Balancing is making the number of atoms of each element same on both the sides (reactant and product side).
To find the number of atoms of each element we multiply coefficient and the subscript
For example
contains
5 × 1 = 5 ,Ca atoms and
5 × 2 = 10, Cl atoms
If there is a bracket in the chemical formula
For example
we multiply coefficient × subscript × number outside the bracket to find the number of atoms
(Please note: 3 is the coefficient, and if there is no number given then 1 will be the coefficient )
So
3 × 3 = 9 , Ca atoms
3 × 1 × 2 = 6, P atoms
3 × 4 × 2 = 24, O atoms are present
Let us balance the equation given

(UNBALANCED)
Reactant side Number of atoms or groups Product side
of each element
3 Ca 1
2 N 2
12 H 8
6 O 2
Multiplying
on the right side by 3, we will have

Reactant side Number of atoms or groups Product side
of each element
3 Ca 3
2 N 2
12 H 12
6 O 6
Balanced!!!!