Question

what will be the balancing for this

Answer 1

for balancing the above equation we have to multiply
2 in kno3 and 2 in kno2

so we have
2KNO3 = 2KNO2 + O2

Answer 2

How to approach balancing of equation

KNO3----->KNO2 + O2

See that the K and N atoms are balanced but the oxygens are not.

There are 3 oxygen atom in the left but 4 in right

So the O2 molecule must be halved to balance it

KNO3----->KNO2 + 1/2 O2

Now its balanced but the Oxygen molecule can not be half

So we multiply each of the substance with 2

So we get

2 KNO3----->2 KNO2 +  O2

Now see its balanced

Hope this helps : )