Are you good with children? Do you like children? Do you have time in the afternoon?

    We need a babysitter for our son. He's five years old. The working time is from Monday to Friday, 3:00 p.m to 6:00 p.m.: pay(薪水) is$ 5 an hour.

    We need help with: Looking after our son, reading to him, playing with him.

    You must work at our house. We live in Fourth Road, near Huaxing Clothes Store. Please call Mr. Wang at 010-58899333.

下列各式﹣3x，$\frac{x+y}{x-y}$，$\frac{xy-y}{3}$，﹣$\frac{3}{10}$，$\frac{2}{5+y}$，$\frac{3}{x}$，$\frac{x}{4xy}$中，分式的个数为（　　）