Asuperhero recently asked his nemesis how many cats she has. she answered with a riddle: "one-half of my cats plus two."
how many cats does the nemesis have?

I got ten. Here's the equation. 

x = 1/2x + 5 

Subtract 1/2x from both sides to get all x's on one side 

x - 1/2x = 1/2x - 1/2x + 5 

1/2x = 5 

Now multiple the left by 2 to get x, but since it's an equation, you need to also multiply the right by 2 to keep it =. 

2 * 1/2x = 2 * 5 

x = 10 cats

31/6= 19/6 19/6 *1/7=19/42