?EA?S has been proved:
From PEARS=3, it can be pe--s, p-a-s, p--rs, -ea-s, -e-rs, --ars.
It can't be p-a-s because of PLANS=2, if it was it would've been 3 as PEARS was 3.
It can't be pe--s, p--rs, -e-rs, or --ars because of PIERS=1, for the S.
Therefore, the only remaining is -ea-s.
[i hope I did this right, it's my first real logic...]