Question

Ln(P2/p1)=ln(-delta Hvap/R)•(1/T1-1/t2)

I have ammonia at normal boil with a temp at 39.2C find the Hvap

Answer 1

So substitute and solve but you need more information than what you've listed.
At normal boil T, whatever that is, P is 760 mm. That gives you p1 and t1. You have a T2 listed at 39.2 C, There should be a p2 to go with that.