Answer:
 .
.
Step-by-step explanation:
Indeed it is possible to solve this problem with system of multiple equations. This explanation will give an approach that gives the same result with less calculations.
Start by finding the most complex species in the equation and setting its coefficient to 
 . That species should as many elements as possible. For example, in this question,
. That species should as many elements as possible. For example, in this question, 
 ,
, 
 , and
, and 
 all contain three elements each. Nonetheless,
 all contain three elements each. Nonetheless, 
 and
 and 
 are more preferable for they contain more atoms.
 are more preferable for they contain more atoms. 
For example, in case 
 is chosen as the most complex species. Set its coefficient to
 is chosen as the most complex species. Set its coefficient to 
 :
:
 .
.
There are two 
 atoms, one
 atoms, one 
 atom, and four
 atom, and four 
 atoms in that
 atoms in that 
 . Since
. Since 
 also contains
 also contains 
 and
 and 
 , it is not certain how many
, it is not certain how many 
 and
 and 
 on the left-hand side in total. However, on the left-hand side,
 on the left-hand side in total. However, on the left-hand side, 
 appears only in
 appears only in 
 . Therefore, it is certain that there is only one
. Therefore, it is certain that there is only one 
 in the left-hand side of the equation.
 in the left-hand side of the equation. 
In chemical reaction, atoms of an element are neither created nor destroyed. Therefore, the number of 
 atoms on the right-hand side should be the same as that on the left-hand side. Therefore, there should also be only one
 atoms on the right-hand side should be the same as that on the left-hand side. Therefore, there should also be only one 
 atom on the right-hand side.
 atom on the right-hand side.
On the right-hand side, 
 is the only compound that contains
 is the only compound that contains 
 . Besides, each formula unit of
. Besides, each formula unit of 
 contains exactly one
 contains exactly one 
 . The only way to get exactly one
. The only way to get exactly one 
 atom on the right-hand side is to set the coefficient of
 atom on the right-hand side is to set the coefficient of 
 to one, as well. The equation will then look like:
 to one, as well. The equation will then look like:
 .
.
With a similar logic, on the right-hand side, 
 is the only species with
 is the only species with 

 atoms. There would be exactly two
 atoms. There would be exactly two 
 atoms on each side of the equation. On the left-hand side,
 atoms on each side of the equation. On the left-hand side, 
 is the only species with
 is the only species with 
 atoms. Each formula unit of
 atoms. Each formula unit of 
 contains one
 contains one 
 atom. Therefore, the coefficient of
 atom. Therefore, the coefficient of 
 should be
 should be 
 .
.
 .
.
It is now certain that there are 
 (six)
 (six) 
 atoms on the left-hand side of the equation. With a similar logic, there should also be six
 atoms on the left-hand side of the equation. With a similar logic, there should also be six 
 atoms on the right-hand side of the equation. Four of these would come from
 atoms on the right-hand side of the equation. Four of these would come from 
 . The other two would come from
. The other two would come from 
 .
. 
Each 
 molecule contains one
 molecule contains one 
 atom. As a result, there needs to be
 atom. As a result, there needs to be 
 (two)
 (two) 
 molecules on the left-hand side.
 molecules on the left-hand side.
Hence the equation:
 .
.
Double-check the work by making sure that the number of 
 atoms is also the same on both sides of the equation.
 atoms is also the same on both sides of the equation.