If you find a first you will be able to find b a little faster then it is super easy after that you got this!
52
- is prime? No
- is multiple of 3? No
continue
53
- is prime? Yes
continue
54
- is prime? No
- is multiple of 3? Yes
- is multiple of 4? No
continue
55
- is prime? No
- is multiple of 3? No
continue
56
- is prime? No
- is multiple of 3? No
continue
57
- is prime? No
- is multiple of 3? Yes
- is multiple of 4? No
continue
58
- is prime? No
- is multiple of 3? No
continue
59
- is prime? Yes
continue
60
- is prime? No
- is multiple of 3? Yes
- is multiple of 4? Yes
Therefore 60 is the answer, as it fits all the conditions
Simple trial and error.
3.5 - 3.2 = 3.8 - 3.5 = 4.1 - 3.8 = 0.3 (common difference)
Exterior angles are complementary to the opposite interior angle