GRE
$$x+y+z$$
$$\frac{1}{x+y+z}$$
The fraction of the garage not painted by Jim and Katrin
19/30
$$\frac{(k+1)!}{(k-1)!}$$
(k)(k+1)
$$\frac{x+y}{2}$$
33
25000 +道题目
236本备考书籍