Why does it take 3 copies of 1/6 to show the same amount as 1/2

Think of a pizza, cut in half. You have one half. If you cut each half into 3 pieces, you'll have a total of 6 pieces, so each piece is 1/6 of the pizza. But each half is made up of 3 1/6 pieces. So, three 1/6 pieces equals one 1/2 pizza.

The correct answer is -4