Using Hess's law to find enthalpy change for N2 formation

[gurpalc]

Homework Statement

http://imgur.com/lb0HL

Homework Equations

in pic

The Attempt at a Solution

So I multiplied the H2 + 1/2O2 equation by 3 and added it to the (N2H4, 2NH3) equation.

I got H2O to match up and O2 to match up, but I don't know how to manipulate the other

equations to get 4N2 to match up. Do I divide all by four? I don't know.
Please help.
Thanks

 

[JohnRC]

please copy and paste the question -- do not link it; I have no way of knowing whether it is a scam link.