GRE
$$\frac{1}{\frac{1}{a}+\frac{1}{15}+\frac{1}{14}+\frac{1}{13}+\frac{1}{12}}$$
$$\frac{1}{\frac{1}{b}+\frac{1}{15}+\frac{1}{14}+\frac{1}{13}+\frac{1}{12}}$$
x
20
$$a^{2}$$+$$(\frac{1}{a})^{2}$$
3
The product of the three roots
-2
y
115
$$a_{20}$$
$$\sqrt{401}$$
The average (arithmetic mean) of the integers from 1 to 31, inclusive
16
s-r
t-s
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