Give the step-by-step reasoning process and then the final answer. A 40-bead necklace is made up of three kinds of beads. There are seven amethyst beads and twice as many amber beads as amethysts. The third beads are turquoise. How many turquoise beads are in the necklace?
There are 7 * 2 = 14 amber beads. Thus, there are 40 - 7 - 14 = 19 turquoise beads in the necklace.
The final answer: 19.