Which of the following doesn't belong?
21-3-18-9-15

9 or 15

Step-by-step explanation:

If you choose 9 to be excluded from the list,

The list should be the following-

21-3-18-3-15

9 should become 3 to make it 15.

The sequence is created like this,

21 - 3 = 18

18 - 3 = 15

If you use 9, the result should be 18 - 9 = 9.

Therefore, if we choose 15 to be excluded from the sequence, the sequence should be-

21-3-18-9-9

So the answer is either 9 or 15.

what graph

step-by-step explanation:

step-by-step explanation:

one of the most important purposes of surface treatment is to alter surface properties according to the requirement of specific applications. for example, hydrophobic coating has been utilized on windshield and eyeglasses. gold atom monolayer on substrate has become a popular surface bioconjugation strategy.