How do I solve this?

I) No, As Restricted is dominant over mallard u cant have mallard ducks with any restricted gene. or else they wont be mallard ducks!
ii) 11+34= 45 11/45 = ~1/4 Punnent square suggests that parents must be M,Md Genotype
| M |Md
M | MM |MMd
Md | MdM |MdMd<----- this is the onli one which is dusky so 1/4

iii)Yes, If you think about it and ii) it comes down to the same answer. We are looking for possibilities of the dusky from restricted but doesnt suggest any type of genotypes
so we can assume that the geno culd be MrMd , MrMr, MdMd yet only the first two are restricted ducks.
Using punnet square and multiple testing u realise that there is a possibility of getting dusky ducks
if you chose the parents geno's as MrMd.
|Mr | Md
Mr |MrMr | MrMd
Md |MdMr |MdMd ---- dusky duck right there!

So yes it is possible with two restricted ducks if at least one has the dusky gene. Remember you can't make something out of nothing, so if no dusky gene no dusky duck possible.