1) The prime factors for 25 are 5 and 5 (5x5 is 25) which add up to 10
26s prime factors are 2 and 13, which equal 15
Finally, 27s factors are 3,3, and 3; which equals 9 ~ 26 is the best option
2) The prime factorization of 27 is 3, 3, 3 - they used 9 and 3 (not the lowest terms)
3) There is more than one way to come up with 36, and only one way for 15 (other than 1) Ex. 8x4=36 & 9x4=36 5x3=15