>I'll be very happy IF Jake comes home tonight.
Not actually faulty, but somewhat odd way to put it. "Better" would be;

I would be very happy if Jake comes home tonight.
or
I will be very happy when Jake comes home tonight.

Can't really place fault with the other two sentences though.

I'll be very happy when Jake comes home tonight.
OR: I would be very happy if Jake came home tonight.
Nora won't find a job unless she tries harder.
We'll go out this afternoon if it doesn't rain.

>>17349511
Okay, the book is being very vague about, it just says that those sentences are wrong and present tense should be used. These are so hard because I feel like all of them sound kind of right and the rules are so weird.

Thise sentences are all correct. If I had to guess, these sentences would all use the subjunctive in your native language; an I right?

English technically has a subjunctive/speculative, but it doesn't get used often nowadays. The sentences you mentioned reflect more common usage patterns.

>>17349518
>present tense should be used
Dude maybe say that right away. It is not so much about what sounds better then but about you learning how to use tenses.

I am very happy that Jake comes home tonight.
Nora does not find a job if she does not try harder.
We are going out this afternoon unless it rains.

>>17349527
Actually it's future tense in sentences that express time or condition in a dependent clause. Don't know the proper word for that mess haha.

>>17349528
Ah I see, thanks a lot! Getting so confused ;_;

>>17349518
I'll be very happy _when_ Jake comes home tonight.

Just match the tenses up.

>>17349541
Hmm not sure if this is right either. I'll just try to find some other book that explains it better.

>>17349541

That doesn't fix anything, it just changes the condition.

All of the sentences in the OP are fine on their own.