hi can you please help me with the first one.

In order to check if the sequence is arithmetic or not, we need to subtract each number by the number before and check if this ratio is always the same. So we have:
27 - 12 = 15
42 - 27 = 15
57 - 42 = 15
72 - 57 = 15
The ratio is always 15, so this sequence is arithmetic, therefore the correct option is the first one.