HNO3 + H2SO4 + NO You now have these half-reaction equations:
3e + HNO3 → NO
S→ H2SO4 + 6e
Which factor will you use for the top equation?
Which factor will you use for the bottom equation?

Explanation:

The two half equations are;

3e + HNO3 → NO

S→ H2SO4 + 6e

When balancing half equations, we have to make sure the number of electrons gained is equal to the number of electrons lost.

Which factor will you use for the top equation?

We multiply by 2 to make the number of electrons =  6e

Which factor will you use for the bottom equation?

We multiply by 1 to make the number of electrons = 6e