Answer
N2O5 + H2O -> 2(HNO3)
Work Step by Step
N2O5 + H2O -> HNO3
First we balance the H since it appears only once on each side so we need to double the right side since there are 2 Hs on the left and only 1 on the right
N2O5 + H2O -> 2(HNO3)
Now we balance the Ns since it also appears only once. We have 2 Ns on the left and 2 on the right so they are balanced.
Last we balance the Os. We have 6 on the left and 6 on the right so it is also balanced.
