15
Prime factorization of 99 = 3 * 3 * 11
3 x 3 x 3 x 5 = 135
3 x 5 x 5 = 75
15 since you multiply by 3 then subtract 3 in sequence
How about: 3 times -6 = -18 as one example
15
They are: 1*18 = 18, 2*9 = 18 and 3*6 = 18
3 x6 =18 2 x9 =18 1 x 18 =18
You can multiply the number 18 by different numbers that are relatively prime, for example by different prime numbers.
-15
Presumably, the theory is that it's easier to multiply by small numbers than larger ones. If there's a number that you need multiplied by 18, multiply it by 3, then multiply that total by 3, then multiply that total by 2.
1 x 18, 2 x 9, 3 x 6
1 x 18, 2 x 9, 3 x 6
21
135
The numbers are: -5 and 3