Answer:
Peter should join Lab thinkers to receive a better deal.
Science buddies costs 190$ for six months.
Lab thinkers costs 170$ for six months.
Explanation:
The equations are...
Science buddies: 10+30x -> 10+30(6)=190
Lab thinkers: 45+25x -> 45+25(6)=170
Peter saves 20$ if he chooses lab thinkers.
Sorry for my mistake, this is my new edit.