1 and 2
Yes
65
This will happen if the fractional parts of the numbers sum to 1.
Two is the minimum number of vectors that will sum to zero.
65
18 and 81
27
The sum of two number times a third numberis equal to the sum of each addend times the third number
That's the distributive property.
Expressed algebraically, this is equal to 52 + x.
28
prime number