WILL & WON'T for agreement and willingness
This exercise tries to shows the difference between the use of WILL as a future and WILL indicating willingness.
In the future, after conjunctions like if, when, before, after, as long as, as soon as, until, unless - just about anything except because - the present tense is correct, hence:
I will tell John when I SEE him. (not "will see")
In sentences where WILL indicates willingness or agreement to do something, or in the negative a refusal, WILL (or WON'T) is used even after the conjunctions listed above (usually IF). Hence:
If Mary won't work next Saturday we'll get Joan to come in.
I will only accept this proposal if you will reduce the price by 10%.
(The WILL is optional in the latter as
I will only accept this proposal if you reduce the price by 10%.
is also correct but the first insists on the proposers willingness to accept a reduction.
In this exercise you should tick those examples where WILL is possible, not just where it is obligatory.
Don't forget that when WHEN is used as a question (and not as a conjunction, the future is used i.e.:
When will I see you again?
Notice this use of "only" and its position in the sentence:
If John will only stop smoking I'm sure his asthma will improve.