Answer:
12
Step-by-step explanation:
2+5=7
7+5=12
Pattern of +5
I assume you're looking for the number:
0.5n + 9 = 21
- 9
0.5n = 12
÷ 0.5
n = 24
So the beginning number is 24, hope this helps!
No. It would be a arithmetic sequence
38-36 =2
36-30 = 6
30-28 = 2
28-22 = 6
so next number would be 22-2 = 20
next number = 20