The answer is 30. You just multiply 51 by (10/17)
P(B|A) = P(B), based on your description, it does not indicate any relationship between A and B, so P(B) is irrelevant with P(A)
An arithmetic sequence has a common difference.
143 - 130 = 13
156 - 143 = 13
169 - 156 = 13
The common difference is 13.
a1 = 130
a2 = 130 + 13
a3 = 130 + 2 * 13
a4 = 130 + 3 * 13
...
an = 130 + (n - 1) * 13
an = 130 + 13(n - 1)
an = 130 + 13n - 13
an = 117 + 13n
an = 13n + 117
The bucket leaks 1/4 ounce per hour. Because the numerator is 3 and it took 3 hours, you can give 1/4 to every hour (3/4 divided by 3).