.
= = = 2*70 = 140.
You place these 2 enemies in different boats by 2 ways,
and then you select 4 of 8 to place in one boat; then the remaining 4 are automatically assigned for the other boat.
On combinations, see the lessons
- Introduction to Combinations
- PROOF of the formula on the number of Combinations
- Problems on Combinations
- OVERVIEW of lessons on Permutations and Combinations
in this site.
Also, you have this free of charge online textbook in ALGEBRA-II in this site
- ALGEBRA-II - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Combinatorics: Combinations and permutations".